diff --git a/api/__init__.py b/api/__init__.py
new file mode 100644
index 0000000..408e40e
--- /dev/null
+++ b/api/__init__.py
@@ -0,0 +1,23 @@
+from .project import have_project, create_project, delete_project
+from .project import is_project_open, open_project, close_project
+from .project import copy_project
+
+from .change_set import ChangeSet
+
+from .operation import execute_undo as undo
+from .operation import execute_redo as redo
+from .operation import have_snapshot, take_snapshot, pick_snapshot
+from .operation import have_transaction, start_transaction, commit_transaction, abort_transaction
+
+from .s0_base import JUNCTION, RESERVOIR, TANK, PIPE, PUMP, VALVE
+from .s0_base import is_node, is_junction, is_reservoir, is_tank
+from .s0_base import is_link, is_pipe, is_pump, is_valve
+from .s0_base import is_curve
+from .s0_base import is_pattern
+from .s0_base import get_nodes, get_links, get_curves, get_patterns
+
+from .s1_title import set_title, get_title
+
+from .s2_junctions import add_junction, delete_junction
+from .s2_junctions import get_junction_elevation, get_junction_demand, get_junction_pattern, get_junction_coord
+from .s2_junctions import set_junction_elevation, set_junction_demand, set_junction_pattern, set_junction_coord
\ No newline at end of file
diff --git a/api/change_set.py b/api/change_set.py
new file mode 100644
index 0000000..efedeff
--- /dev/null
+++ b/api/change_set.py
@@ -0,0 +1,14 @@
+class ChangeSet:
+    def __init__(self) -> None:
+        self.added : list[dict[str, str]] = {}
+        self.deleted : list[dict[str, str]] = {}
+        self.updated : list[dict[str, str]] = {}
+
+    def add(self, type: str, id: str) -> None:
+        self.added.append({ 'type': type, 'id': id })
+
+    def delete(self, type: str, id: str) -> None:
+        self.deleted.append({ 'type': type, 'id': id })
+
+    def update(self, type: str, id: str, property: str) -> None:
+        self.updated.append({ 'type': type, 'id': id, 'property': property })
\ No newline at end of file
diff --git a/api/connection.py b/api/connection.py
new file mode 100644
index 0000000..b42b481
--- /dev/null
+++ b/api/connection.py
@@ -0,0 +1,3 @@
+import psycopg as pg
+
+g_conn_dict : dict[str, pg.Connection] = {}
\ No newline at end of file
diff --git a/api/operation.py b/api/operation.py
new file mode 100644
index 0000000..ac457f3
--- /dev/null
+++ b/api/operation.py
@@ -0,0 +1,220 @@
+from psycopg.rows import dict_row, Row
+from .connection import g_conn_dict as conn
+
+def _get_current_transaction(name: str) -> Row | None:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select * from transaction_operation")
+        return cur.fetchone()
+
+def _get_current_transaction_id(name: str) -> int:
+    row = _get_current_transaction(name)
+    return int(row['id'])
+
+def _remove_transaction(name: str) -> None:
+    with conn[name].cursor() as cur:
+        cur.execute(f"delete from transaction_operation")
+
+def _remove_operation(name: str, id: int) -> None:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        # can not be >= to cascade delete since there is a tree !
+        cur.execute(f"delete from transaction_operation where id = {id}") # this should not happen
+        cur.execute(f"delete from snapshot_operation where id = {id}") # this may happen
+        cur.execute(f"delete from operation where id = {id}")
+
+def _get_parents(name: str, id: int) -> list[int]:
+    ids = [id]
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        while ids[-1] != 0:
+            cur.execute(f"select parent from operation where id = {ids[-1]}")
+            ids.append(int(cur.fetchone()['parent']))
+    return ids
+
+def _get_current_operation(name: str) -> int:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select id from current_operation")
+        return int(cur.fetchone()['id'])
+
+def _update_current_operation(name: str, old_id: int, id: int) -> None:
+    with conn[name].cursor() as cur:
+        cur.execute(f"update current_operation set id = {id} where id = {old_id}")
+
+def _add_redo_undo(name: str, redo: str, undo: str) -> int:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        parent = _get_current_operation(name)
+        cur.execute(f"insert into operation (id, redo, undo, parent) values (default, '{redo}', '{undo}', {parent})")
+        cur.execute("select max(id) from operation")
+        return int(cur.fetchone()['max'])
+
+# execute curr undo
+def _query_undo(name: str, id: str) -> dict[str, str]:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select undo, parent from operation where id = {id}")
+        return cur.fetchone()
+
+# execute next redo
+def _query_redo_child(name: str, id: str) -> str:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select redo_child from operation where id = {id}")
+        return cur.fetchone()['redo_child']
+
+def _query_redo(name: str, id: str) -> dict[str, str]:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select redo from operation where id = {id}")
+        return cur.fetchone()['redo']
+
+def _set_redo_child(name: str, id: int, child: int | str) -> None:
+    with conn[name].cursor() as cur:
+        cur.execute(f"update operation set redo_child = {child} where id = {id}")
+
+def _execute(name: str, sql: str) -> None:
+    with conn[name].cursor() as cur:
+        sql = sql.replace("\"", "\'")
+        cur.execute(sql)
+
+def add_operation(name: str, redo: str, undo: str) -> None:
+    curr = _add_redo_undo(name, redo, undo)
+    old = _get_current_operation(name)
+    _update_current_operation(name, old, curr)
+
+def execute_undo(name: str, discard: bool = False) -> None:
+    curr = _get_current_operation(name)
+
+    # transaction control
+    if have_transaction(name):
+        tran = _get_current_transaction(name)
+        if tran != None and int(tran['id']) >= 0:
+            if bool(tran['strict']): # strict mode disallow undo
+                print("Do not allow to undo in strict transaction mode!")
+                return
+            elif int(tran['id']) >= curr: # normal mode disallow undo start point, and there is foreign key constraint
+                print("Do not allow to undo transaction start point!")
+                return
+
+    row = _query_undo(name, curr)
+    undo = row['undo']
+    if undo == '':
+        print("nothing to undo!")
+        return
+
+    parent = int(row['parent'])
+    _set_redo_child(name, parent, 'NULL' if discard else curr)
+
+    _execute(name, undo)
+    _update_current_operation(name, curr, parent)
+
+    if discard:
+        _remove_operation(name, curr)
+
+def execute_redo(name: str) -> None:
+    curr = _get_current_operation(name)
+    redoChild = _query_redo_child(name, curr)
+    if redoChild == None:
+        print("nothing to redo!")
+        return
+    
+    child = int(redoChild)
+    redo = _query_redo(name, child)
+
+    _execute(name, redo)
+    _update_current_operation(name, curr, child)
+
+# snapshot support to checkout between different version of database
+# snapshot is persistent
+# since redo always remember the recently undo path
+
+def have_snapshot(name: str, tag: str) -> bool:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select id from snapshot_operation where tag = '{tag}'")
+        return cur.rowcount > 0
+
+def take_snapshot(name: str, tag: str) -> None:
+    if tag == None or tag == '':
+        print('Non empty tag is expected!')
+        return
+
+    curr = _get_current_operation(name)
+
+    with conn[name].cursor() as cur:
+        cur.execute(f"insert into snapshot_operation (id, tag) values ({curr}, '{tag}')")
+
+def pick_snapshot(name: str, tag: str) -> None:
+    if tag == None or tag == '':
+        print('Non empty tag is expected!')
+        return
+
+    if not have_snapshot(name, tag):
+        print('No such snapshot!')
+        return
+
+    curr = _get_current_operation(name)
+    curr_parents = _get_parents(name, curr)
+
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select id from snapshot_operation where tag = '{tag}'")
+        target = int(cur.fetchone()['id'])
+        if target in curr_parents: # target -> curr
+            for i in range(curr_parents.index(target)):
+                execute_undo(name)
+        else:
+            target_parents = _get_parents(name, target)
+            if curr in target_parents: # curr -> target
+                for i in range(target_parents.index(curr)):
+                    execute_redo(name)
+            else:
+                ancestor_index = -1
+                while curr_parents[ancestor_index] == target_parents[ancestor_index]:
+                    ancestor_index -= 1
+
+                # ancestor -> curr
+                ancestor = curr_parents[ancestor_index + 1] # ancestor_index + 1 is common parent
+                for i in range(curr_parents.index(ancestor)):
+                    execute_undo(name)
+                # ancestor -> redo, need assign redo_child
+                while target_parents[ancestor_index] != target:
+                    cur.execute(f"update operation set redo_child = '{target_parents[ancestor_index]}' where id = '{target_parents[ancestor_index + 1]}'")
+                    execute_redo(name)
+                    ancestor_index -= 1
+                cur.execute(f"update operation set redo_child = '{target}' where id = '{target_parents[1]}'")
+                execute_redo(name)
+
+# transaction is volatile, commit/abort will destroy transaction.
+# can not redo an aborted transaction.
+# but can undo a committed transaction... inconsistent...
+# it may remove snapshot if it is in aborted transaction
+
+def have_transaction(name: str) -> bool:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select * from transaction_operation")
+        return cur.rowcount > 0
+
+def start_transaction(name: str, strict: bool = False) -> None:
+    if have_transaction(name):
+        print("Only support single transaction now, please commit/abort current transaction!")
+        return
+
+    curr = _get_current_operation(name)
+
+    with conn[name].cursor() as cur:
+        cur.execute(f"insert into transaction_operation (id, strict) values ({curr}, {strict});")
+
+def commit_transaction(name: str) -> None:
+    if not have_transaction(name):
+        print("No active transaction!")
+        return
+
+    _remove_transaction(name)
+
+def abort_transaction(name: str) -> None:
+    if not have_transaction(name):
+        print("No active transaction!")
+        return
+
+    tran = _get_current_transaction_id(name)
+
+    curr = _get_current_operation(name)
+    curr_parents = _get_parents(name, curr)
+
+    for i in range(curr_parents.index(tran)):
+        execute_undo(name, True)
+    
+    _remove_transaction(name)
diff --git a/api/project.py b/api/project.py
new file mode 100644
index 0000000..f283c85
--- /dev/null
+++ b/api/project.py
@@ -0,0 +1,33 @@
+import psycopg as pg
+from .connection import g_conn_dict as conn
+
+# no undo/redo
+
+def have_project(name: str) -> bool:
+    with pg.connect(conninfo="dbname=postgres", autocommit=True) as conn:
+        with conn.cursor() as cur:
+            cur.execute(f"select * from pg_database where datname = '{name}'")
+            return cur.rowcount > 0
+
+def copy_project(source: str, new: str) -> None:
+    with pg.connect(conninfo="dbname=postgres", autocommit=True) as conn:
+        with conn.cursor() as cur:
+            cur.execute(f"create database {new} with template = {source}")
+
+def create_project(name: str) -> None:
+    return copy_project('project', name)
+
+def delete_project(name: str) -> None:
+    with pg.connect(conninfo="dbname=postgres", autocommit=True) as conn:
+        with conn.cursor() as cur:
+            cur.execute(f"drop database {name}")
+
+def open_project(name: str) -> None:
+    conn[name] = pg.connect(conninfo=f"dbname={name}", autocommit=True)
+
+def is_project_open(name: str) -> bool:
+    return name in conn
+
+def close_project(name: str) -> None:
+    conn[name].close()
+    del conn[name]
diff --git a/api/s0_base.py b/api/s0_base.py
new file mode 100644
index 0000000..87350a7
--- /dev/null
+++ b/api/s0_base.py
@@ -0,0 +1,75 @@
+from psycopg.rows import dict_row, Row
+from .connection import g_conn_dict as conn
+
+_NODE = "_node"
+_LINK = "_link"
+_CURVE = "_curve"
+_PATTERN = "_pattern"
+
+JUNCTION = "JUNCTION"
+RESERVOIR = "RESERVOIR"
+TANK = "TANK"
+PIPE = "PIPE"
+PUMP = "PUMP"
+VALVE = "VALVE"
+
+def _get_from(name: str, id: str, base_type: str) -> Row | None:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select * from {base_type} where id = '{id}'")
+        return cur.fetchone()
+
+def is_node(name: str, id: str) -> bool:
+    return _get_from(name, id, _NODE) != None
+
+def is_junction(name: str, id: str) -> bool:
+    row = _get_from(name, id, _NODE)
+    return row != None and row['type'] == JUNCTION
+
+def is_reservoir(name: str, id: str) -> bool:
+    row = _get_from(name, id, _NODE)
+    return row != None and row['type'] == RESERVOIR
+
+def is_tank(name: str, id: str) -> bool:
+    row = _get_from(name, id, _NODE)
+    return row != None and row['type'] == TANK
+
+def is_link(name: str, id: str) -> bool:
+    return _get_from(name, id, _LINK) != {}
+
+def is_pipe(name: str, id: str) -> bool:
+    row = _get_from(name, id, _LINK)
+    return row != None and row['type'] == PIPE
+
+def is_pump(name: str, id: str) -> bool:
+    row = _get_from(name, id, _LINK)
+    return row != None and row['type'] == PUMP
+
+def is_valve(name: str, id: str) -> bool:
+    row = _get_from(name, id, _LINK)
+    return row != None and row['type'] == VALVE
+
+def is_curve(name: str, id: str) -> bool:
+    return _get_from(name, id, _CURVE) != None
+
+def is_pattern(name: str, id: str) -> bool:
+    return _get_from(name, id, _PATTERN) != None
+
+def _get_all(name: str, base_type: str) -> list[str]:
+    ids : list[str] = []
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select id from {base_type} order by id")
+        for record in cur:
+            ids.append(record['id'])
+    return ids
+
+def get_nodes(name: str) -> list[str]:
+    return _get_all(name, _NODE)
+
+def get_links(name: str) -> list[str]:
+    return _get_all(name, _LINK)
+
+def get_curves(name: str) -> list[str]:
+    return _get_all(name, _CURVE)
+
+def get_patterns(name: str) -> list[str]:
+    return _get_all(name, _PATTERN)
diff --git a/api/s1_title.py b/api/s1_title.py
new file mode 100644
index 0000000..3d0e3a3
--- /dev/null
+++ b/api/s1_title.py
@@ -0,0 +1,24 @@
+from psycopg.rows import dict_row
+from .operation import *
+from .connection import g_conn_dict as conn
+from .change_set import ChangeSet
+
+def get_title(name: str) -> str:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select * from title")
+        return cur.fetchone()['value']
+
+def set_title(name: str, value: str) -> ChangeSet:
+    old = get_title(name)
+
+    with conn[name].cursor() as cur:
+        sql = f"update title set value = '{value}'"
+        cur.execute(sql)
+
+        redo = sql.replace("'", '"')
+        undo = f'update title set value = "{old}"'
+        add_operation(name, redo, undo)
+
+    change = ChangeSet()
+    change.update('title', 'null', 'value')
+    return change
diff --git a/api/s2_junctions.py b/api/s2_junctions.py
new file mode 100644
index 0000000..0c77405
--- /dev/null
+++ b/api/s2_junctions.py
@@ -0,0 +1,188 @@
+from psycopg.rows import dict_row, Row
+from .connection import g_conn_dict as conn
+from .s0_base import *
+from .operation import *
+from .change_set import ChangeSet
+
+def add_junction(name: str, id: str, x: float, y: float, elevation: float) -> ChangeSet:
+    if is_node(name, id):
+        return
+
+    with conn[name].cursor() as cur:
+        sql = f"insert into _node (id, type) values ('{id}', 'JUNCTION');"
+        sql += f" insert into junctions (id, elevation) values ('{id}', {elevation});"
+        sql += f" insert into coordinates (node, coord) values ('{id}', '({x}, {y})');"
+        cur.execute(sql)
+
+        redo = sql.replace("'", '"')
+        undo = f'delete from coordinates where node = "{id}";'
+        undo += f' delete from junctions where id = "{id}";'
+        undo += f' delete from _node where id = "{id}";'
+        add_operation(name, redo, undo)
+
+    change = ChangeSet()
+    change.add('junction', id)
+    return change
+
+
+def delete_junction(name: str, id: str) -> ChangeSet:
+    if not is_junction(name, id):
+        return
+
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select * from junctions where id = '{id}'")
+        row = cur.fetchone()
+        if row == None:
+            return
+
+        elevation = row['elevation']
+        demand = 'NULL' if row['demand'] == None else row['demand']
+        pattern = 'NULL' if row['pattern'] == None else row['pattern']
+        pattern = f'"{pattern}"' if pattern != 'NULL' else pattern
+
+        cur.execute(f"select * from coordinates where id = '{id}'")
+        row = cur.fetchone()
+        if row == None:
+            return
+
+        coord = row['coord']
+
+        sql = f"delete from coordinates where node = '{id}';"
+        sql += f" delete from junctions where id = '{id}';"
+        sql += f" delete from _node where id = '{id}';"
+        cur.execute(sql)
+
+        redo = sql.replace("'", '"')
+        undo = f'insert into _node (id, type) values ("{id}", "{type}");'
+        undo += f" insert into junctions (id, elevation, demand, pattern) values ('{id}', {elevation}, {demand}, {pattern});"
+        undo += f"  insert into coordinates (node, coord) values ('{id}', '{coord}');"
+        add_operation(name, redo, undo)
+
+    change = ChangeSet()
+    change.delete('junction', id)
+    return change
+
+
+def _get_junction(name: str, id: str) -> Row | None:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select elevation, demand, pattern from junctions where id = '{id}'")
+        return cur.fetchone()
+
+def get_junction_elevation(name: str, id: str) -> float | None:
+    row = _get_junction(name, id)
+    return float(row['elevation']) if row != None else None
+
+def get_junction_demand(name: str, id: str) -> float | str | None:
+    row = _get_junction(name, id)
+    if row != None:
+        return float(row['demand']) if row['demand'] != None else 'NULL'
+    else:
+        return None
+
+def get_junction_pattern(name: str, id: str) -> str | None:
+    row = _get_junction(name, id)
+    if row != None:
+        return row['pattern'] if row['pattern'] != None else 'NULL'
+    else:
+        return None
+
+def _to_point(coord: str) -> dict[str, float]:
+    coord = coord.removeprefix('(')
+    coord = coord.removesuffix(')')
+    coord = coord.split(',')
+    return { 'x': float(coord[0]), 'y': float(coord[1]) }
+
+def get_junction_coord(name: str, id: str) -> dict[str, float] | None:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select * from coordinates where node = '{id}'")
+        row = cur.fetchone()
+        if row == None:
+            return None
+        
+        coord = str(row['coord'])
+        return _to_point(coord)
+
+def set_junction_elevation(name: str, id: str, elevation: float) -> ChangeSet:
+    if not is_junction(name, id):
+        return
+
+    old = get_junction_elevation(name, id)
+    if old == None:
+        return
+
+    with conn[name].cursor() as cur:
+        sql = f"update junctions set elevation = {elevation} where id = '{id}'"
+        cur.execute(sql)
+        redo = sql.replace("'", '"')
+        undo = f'update junctions set elevation = {old} where id = "{id}"'
+        add_operation(name, redo, undo)
+
+    change = ChangeSet()
+    change.update('junction', id, 'elevation')
+    return change
+
+
+def set_junction_demand(name: str, id: str, demand: float) -> ChangeSet:
+    if not is_junction(name, id):
+        return
+
+    old = get_junction_demand(name, id)
+    if old == None:
+        return
+
+    with conn[name].cursor() as cur:
+        sql = f"update junctions set demand = {demand} where id = '{id}'"
+        cur.execute(sql)
+        redo = sql.replace("'", '"')
+        undo = f'update junctions set demand = {old} where id = "{id}"'
+        add_operation(name, redo, undo)
+
+    change = ChangeSet()
+    change.update('junction', id, 'demand')
+    return change
+
+
+def set_junction_pattern(name: str, id: str, pattern: str) -> ChangeSet:
+    if not is_junction(name, id):
+        return
+    if not is_pattern(name, id):
+        return
+
+    old = get_junction_pattern(name, id)
+    if old == None:
+        return
+
+    old = f'"{old}"' if old != 'NULL' else old
+
+    with conn[name].cursor() as cur:
+        sql = f"update junctions set pattern = '{pattern}' where id = '{id}'"
+        cur.execute(sql)
+        redo = sql.replace("'", '"')
+        undo = f'update junctions set pattern = {old} where id = "{id}"'
+        add_operation(name, redo, undo)
+
+    change = ChangeSet()
+    change.update('junction', id, 'pattern')
+    return change
+
+
+def set_junction_coord(name: str, id: str, x: float, y: float) -> ChangeSet:
+    if not is_junction(name, id):
+        return
+
+    old = get_junction_coord(name, id)
+    if old == None:
+        return
+    old_x, old_y = old['x'], old['y']
+
+    with conn[name].cursor() as cur:
+        sql = f"update coordinates set coord = '({x},{y})' where node = '{id}'"
+        cur.execute(sql)
+
+        redo = sql.replace("'", '"')
+        undo = f'update coordinates set coord = "({old_x},{old_y})" where node = "{id}"'
+        add_operation(name, redo, undo)
+
+    change = ChangeSet()
+    change.update('junction', id, 'coord')
+    return change
diff --git a/new_demo.py b/new_demo.py
new file mode 100644
index 0000000..02f25d8
--- /dev/null
+++ b/new_demo.py
@@ -0,0 +1,184 @@
+from tjnetwork_new import *
+
+
+def demo_snapshot():
+    p = "demo_snapshot"
+
+    print(p)
+
+    if is_project_open(p):
+        close_project(p)
+
+    if have_project(p):
+        delete_project(p)
+
+    create_project(p)
+    open_project(p)
+
+    add_junction(p, 'j-1', 10.0, 20.0, 30.0)
+    add_junction(p, 'j-2', 10.0, 20.0, 30.0)
+    add_junction(p, 'j-3', 10.0, 20.0, 30.0)
+    add_junction(p, 'j-4', 10.0, 20.0, 30.0)
+    take_snapshot(p, "1-2-3-4")
+
+    undo(p)
+    undo(p)
+    undo(p)
+    undo(p)
+
+    add_junction(p, 'j-5', 10.0, 20.0, 30.0)
+    add_junction(p, 'j-6', 10.0, 20.0, 30.0) 
+    add_junction(p, 'j-7', 10.0, 20.0, 30.0) 
+    add_junction(p, 'j-8', 10.0, 20.0, 30.0)
+    take_snapshot(p, "5-6-7-8")
+
+    print("before checkout, it should be 5, 6, 7, 8")
+    print(get_nodes(p))
+
+    pick_snapshot(p, "1-2-3-4")
+
+    print("after checkout, it should be 1, 2, 3, 4")
+    print(get_nodes(p))
+
+    close_project(p)
+    # delete_project(p)
+
+
+def demo_transaction():
+    p = "demo_transaction"
+
+    print(p)
+
+    if is_project_open(p):
+        close_project(p)
+
+    if have_project(p):
+        delete_project(p)
+
+    create_project(p)
+    open_project(p)
+
+    add_junction(p, 'j-1', 10.0, 20.0, 30.0)
+    take_snapshot(p, "1")
+    add_junction(p, 'j-2', 10.0, 20.0, 30.0)
+    take_snapshot(p, "2")
+
+    start_transaction(p)
+
+    add_junction(p, 'j-3', 10.0, 20.0, 30.0)
+    take_snapshot(p, "3")
+    add_junction(p, 'j-4', 10.0, 20.0, 30.0)
+    take_snapshot(p, "4")
+
+    print("before rollback, it should be 1, 2, 3, 4")
+    print(get_nodes(p))
+
+    print("after rollback, it should be 1, 2")
+    abort_transaction(p)
+
+    print(get_nodes(p))
+
+    print(f"have snapshot 1: {have_snapshot(p, '1')}")
+    print(f"have snapshot 2: {have_snapshot(p, '2')}")
+    print(f"have snapshot 3: {have_snapshot(p, '3')}")
+    print(f"have snapshot 4: {have_snapshot(p, '4')}")
+
+    close_project(p)
+    # delete_project(p)
+
+
+def demo_1_title():
+    p = "demo_1_title"
+
+    print(p)
+
+    if is_project_open(p):
+        close_project(p)
+
+    if have_project(p):
+        delete_project(p)
+
+    create_project(p)
+    open_project(p)
+
+    print(get_title(p)) # 
+
+    set_title(p, "title")
+    print(get_title(p)) # title
+
+    set_title(p, "test")
+    print(get_title(p)) # test
+
+    undo(p)
+    print(get_title(p)) # title
+
+    undo(p)
+    print(get_title(p)) # 
+
+    close_project(p)
+    # delete_project(p)
+
+
+def demo_2_junctions():
+    p = "demo_2_junctions"
+
+    print(p)
+
+    if is_project_open(p):
+        close_project(p)
+
+    if have_project(p):
+        delete_project(p)
+
+    create_project(p)
+    open_project(p)
+
+    j = 'j-1'
+    print(get_junction_coord(p, j)) # None
+    print(get_junction_elevation(p, j)) # None
+    print(get_junction_demand(p, j)) # None
+    print(get_junction_pattern(p, j)) # None
+
+    add_junction(p, j, 10.0, 20.0, 30.0) 
+    print(get_junction_coord(p, j)) # {'x': 10.0, 'y': 20.0}
+    print(get_junction_elevation(p, j)) # 30.0
+    print(get_junction_demand(p, j)) # NULL
+    print(get_junction_pattern(p, j)) # NULL
+
+    set_junction_demand(p, j, 100.0)
+    print(get_junction_demand(p, j)) # 100.0
+
+    undo(p)
+    print(get_junction_demand(p, j)) # NULL
+
+    undo(p)
+    print(get_junction_coord(p, j)) # None
+    print(get_junction_elevation(p, j)) # None
+    print(get_junction_demand(p, j)) # None
+    print(get_junction_pattern(p, j)) # None
+
+    add_junction(p, j, 10.0, 20.0, 30.0)
+    print(get_junction_coord(p, j)) # {'x': 10.0, 'y': 20.0}
+    print(get_junction_elevation(p, j)) # 30.0
+    print(get_junction_demand(p, j)) # NULL
+    print(get_junction_pattern(p, j)) # NULL
+
+    set_junction_coord(p, j, 100.0, 200.0)
+    print(get_junction_coord(p, j)) # {'x': 100.0, 'y': 200.0}
+
+    undo(p)
+    print(get_junction_coord(p, j)) # {'x': 10.0, 'y': 20.0}
+
+    redo(p)
+    print(get_junction_coord(p, j)) # {'x': 100.0, 'y': 200.0}
+
+    close_project(p)
+    # delete_project(p)
+
+
+if __name__ == "__main__":
+    demo_snapshot()
+    demo_transaction()
+    demo_1_title()
+    demo_2_junctions()
+    pass
diff --git a/script/admin.py b/script/admin.py
deleted file mode 100644
index 74d7066..0000000
--- a/script/admin.py
+++ /dev/null
@@ -1,5 +0,0 @@
-from tjnetwork_admin import *
-
-if __name__ == "__main__":
-    delete_template()
-    create_template()
diff --git a/script/script/api/create/1.title.sql b/script/script/api/create/1.title.sql
new file mode 100644
index 0000000..fb81579
--- /dev/null
+++ b/script/script/api/create/1.title.sql
@@ -0,0 +1,27 @@
+-- get_title()
+create function tj.get_title() returns text as
+$$
+declare
+    title text;
+begin
+    select value into title from tj.title;
+    return title;
+end;
+$$ language plpgsql;
+
+-- set_title()
+create function tj.set_title(new_title text) returns void as
+$$
+declare
+    old_title text;
+    redo text;
+    undo text;
+begin
+    select tj.get_title() into old_title;
+    update tj.title set value = new_title where value = old_title;
+
+    redo := concat('update tj.title set value = ''', new_title, ''' where value = ''', old_title, '''');
+    undo := concat('update tj.title set value = ''', old_title, ''' where value = ''', new_title, '''');
+    perform tj.add_operation(redo, undo);
+end;
+$$ language plpgsql;
diff --git a/script/script/api/create/operation.sql b/script/script/api/create/operation.sql
new file mode 100644
index 0000000..ad56cdf
--- /dev/null
+++ b/script/script/api/create/operation.sql
@@ -0,0 +1,109 @@
+create function tj.add_operation(redo text, undo text) returns void as
+$$
+declare
+    parent_id int;
+    curr_id int;
+begin
+    select id into parent_id from tj.current_operation;
+    insert into tj.operation (id, redo, undo, parent) values (default, redo, undo, parent_id);
+    select max(id) into curr_id from tj.operation;
+    update tj.current_operation set id = curr_id where id = parent_id;
+end;
+$$ language plpgsql;
+
+create function tj.have_transaction() returns boolean as
+$$
+declare
+    tran_count int;
+begin
+    select count(*) into tran_count from tj.transaction_operation;
+    return tran_count > 0;
+end;
+$$ language plpgsql;
+
+create function tj.execute_undo(discard boolean) returns void as
+$$
+declare
+    curr_id int;
+    have_tran boolean;
+    tran_id int;
+    strict_mode boolean;
+    undo_sql text;
+    parent_id int;
+begin
+    select id into curr_id from tj.current_operation;
+
+    select tj.have_transaction() into have_tran;
+    if have_tran then
+        select strict into strict_mode from tj.transaction_operation;
+        if strict_mode then
+            return; -- strict mode disallow undo
+        else
+            select id into tran_id from tj.transaction_operation;
+            if tran_id >= curr_id then
+                return; -- # normal mode disallow undo start point, and there is foreign key constraint
+            end if;
+        end if;
+    end if;
+
+    select undo into undo_sql from tj.operation where id = curr_id;
+    if undo_sql = '' then
+        return;
+    end if;
+
+    select parent into parent_id from tj.operation where id = curr_id;
+    if discard then
+        update tj.operation set redo_child = null where id = parent_id;
+    else
+        update tj.operation set redo_child = curr_id where id = parent_id;
+    end if;
+
+    execute undo_sql;
+
+    update tj.current_operation set id = parent_id where id = curr_id;
+
+    if discard then
+        delete from tj.transaction_operation where id = curr_id;
+        delete from tj.snapshot_operation where id = curr_id;
+        delete from tj.operation where id = curr_id;
+    end if;
+end;
+$$ language plpgsql;
+
+create function tj.undo() returns void as
+$$
+declare
+begin
+    perform tj.execute_undo(false);
+end;
+$$ language plpgsql;
+
+create function tj.discard_undo() returns void as
+$$
+declare
+begin
+    perform tj.execute_undo(true);
+end;
+$$ language plpgsql;
+
+create function tj.redo() returns void as
+$$
+declare
+    curr_id int;
+    child_id int;
+    redo_sql text;
+begin
+    select id into curr_id from tj.current_operation;
+
+    select redo_child into child_id from tj.operation where id = curr_id;
+    if child_id = null then
+        return;
+    end if;
+
+    select redo into redo_sql from tj.operation where id = child_id;
+
+    execute redo_sql;
+
+    update tj.current_operation set id = child_id where id = curr_id;
+end;
+$$ language plpgsql;
\ No newline at end of file
diff --git a/script/script/api/create/project.sql b/script/script/api/create/project.sql
new file mode 100644
index 0000000..50e8197
--- /dev/null
+++ b/script/script/api/create/project.sql
@@ -0,0 +1,9 @@
+create function tj.have_project(in_name text) returns boolean as
+$$
+declare
+    db_count int;
+begin
+    select count(*) into db_count from pg_database where datname = in_name;
+    return db_count > 0;
+end;
+$$ language plpgsql;
diff --git a/script/script/api/drop/1.title.sql b/script/script/api/drop/1.title.sql
new file mode 100644
index 0000000..9bef302
--- /dev/null
+++ b/script/script/api/drop/1.title.sql
@@ -0,0 +1,3 @@
+drop function if exists tj.set_title;
+
+drop function if exists tj.get_title;
\ No newline at end of file
diff --git a/script/script/api/drop/operation.sql b/script/script/api/drop/operation.sql
new file mode 100644
index 0000000..1692da5
--- /dev/null
+++ b/script/script/api/drop/operation.sql
@@ -0,0 +1,9 @@
+drop function if exists tj.redo;
+
+drop function if exists tj.discard_undo;
+drop function if exists tj.undo;
+drop function if exists tj.execute_undo;
+
+drop function if exists tj.have_transaction;
+
+drop function if exists tj.add_operation;
\ No newline at end of file
diff --git a/script/script/api/plpgsql.sql b/script/script/api/plpgsql.sql
new file mode 100644
index 0000000..06c96e0
--- /dev/null
+++ b/script/script/api/plpgsql.sql
@@ -0,0 +1,6 @@
+create function xxx() returns void as
+$$
+declare
+begin
+end;
+$$ language plpgsql;
\ No newline at end of file
diff --git a/script/script/table/create/0.base.sql b/script/script/table/create/0.base.sql
new file mode 100644
index 0000000..91b48c0
--- /dev/null
+++ b/script/script/table/create/0.base.sql
@@ -0,0 +1,35 @@
+create type tj.node_type as enum
+(
+  'junction'
+, 'reservoir'
+, 'tank'
+);
+
+create type tj.link_type as enum
+(
+  'pipe'
+, 'pump'
+, 'valve'
+);
+
+create table tj.node
+(
+  id varchar(32) primary key
+, type tj.node_type  not null
+);
+
+create table tj.link
+(
+  id varchar(32) primary key
+, type tj.link_type  not null
+);
+
+create table tj.curve
+(
+  id varchar(32) primary key
+);
+
+create table tj.pattern
+(
+  id varchar(32) primary key
+);
diff --git a/script/script/table/create/1.title.sql b/script/script/table/create/1.title.sql
new file mode 100644
index 0000000..8ba6426
--- /dev/null
+++ b/script/script/table/create/1.title.sql
@@ -0,0 +1,8 @@
+-- [title]
+
+create table tj.title
+(
+  value text
+);
+
+insert into tj.title (value) values ('');
diff --git a/script/script/table/create/10.status.sql b/script/script/table/create/10.status.sql
new file mode 100644
index 0000000..c736c76
--- /dev/null
+++ b/script/script/table/create/10.status.sql
@@ -0,0 +1,33 @@
+-- [status]
+
+create type tj.status_pipe_pump_status as enum
+(
+  'open'
+, 'closed'
+);
+
+create table tj.status_pipe
+(
+  id varchar(32) primary key references tj.pipes(id)
+, status tj.status_pipe_pump_status not null
+);
+
+create table tj.status_pump
+(
+  id varchar(32) primary key references tj.pumps(id)
+, status tj.status_pipe_pump_status not null
+);
+
+create type tj.status_valve_status as enum ('open', 'closed', 'active');
+
+create table tj.status_valve
+(
+  id varchar(32) primary key references tj.valves(id)
+, status tj.status_valve_status not null
+);
+
+create table tj.status_link
+(
+  id varchar(32) primary key references tj.link(id)
+, setting numeric not null
+);
diff --git a/script/script/table/create/11.patterns.sql b/script/script/table/create/11.patterns.sql
new file mode 100644
index 0000000..8cd9ad6
--- /dev/null
+++ b/script/script/table/create/11.patterns.sql
@@ -0,0 +1,7 @@
+-- [patterns]
+
+create table tj.patterns
+(
+  id varchar(32) references tj.pattern(id) not null
+, multipliers numeric not null
+);
diff --git a/script/script/table/create/12.curves.sql b/script/script/table/create/12.curves.sql
new file mode 100644
index 0000000..2467450
--- /dev/null
+++ b/script/script/table/create/12.curves.sql
@@ -0,0 +1,8 @@
+-- [curves]
+
+create table tj.curves
+(
+  id varchar(32) references tj.curve(id) not null
+, x numeric not null
+, y numeric not null
+);
diff --git a/script/script/table/create/13.controls.sql b/script/script/table/create/13.controls.sql
new file mode 100644
index 0000000..ab34bb0
--- /dev/null
+++ b/script/script/table/create/13.controls.sql
@@ -0,0 +1,30 @@
+-- [controls]
+
+create type tj.controls_1_prep as enum ('above', 'below');
+
+-- link  linkid  status  if node   nodeid  above / below   value
+create table tj.controls_1
+(
+  linkid varchar(32) primary key references tj.link(id)
+, status text not null -- open / closed, a pump speed setting, or a control valve setting
+, nodeid varchar(32) references tj.node(id) not null
+, prep tj.controls_1_prep not null
+, value numeric not null
+);
+
+--  link linkid   status   at time  time
+create table tj.controls_2
+(
+  linkid varchar(32) primary key references tj.link(id)
+, status text not null -- open / closed, a pump speed setting, or a control valve setting
+, time interval hour
+);
+
+--  link linkid   status   at clocktime clocktime   am / pm
+create table tj.controls_3
+(
+  linkid varchar(32) primary key references tj.link(id)
+, status text not null -- open / closed, a pump speed setting, or a control valve setting
+, clocktimehour interval hour -- get am/pm from it
+, clocktimemin  interval minute
+);
diff --git a/script/script/table/create/14.rules.sql b/script/script/table/create/14.rules.sql
new file mode 100644
index 0000000..617da6b
--- /dev/null
+++ b/script/script/table/create/14.rules.sql
@@ -0,0 +1,6 @@
+-- [rules]
+
+create table tj.rules
+(
+  content text primary key
+);
diff --git a/script/script/table/create/15.energy.sql b/script/script/table/create/15.energy.sql
new file mode 100644
index 0000000..1544968
--- /dev/null
+++ b/script/script/table/create/15.energy.sql
@@ -0,0 +1,29 @@
+-- [energy]
+
+create type tj.energy_param as enum
+(
+  'price'
+, 'pattern'
+, 'effic'
+);
+
+-- global   price / pattern / effic   value
+create table tj.energy_global
+(
+  param tj.energy_param not null
+, value numeric not null
+);
+
+-- pump  pumpid   price / pattern / effic  value
+create table tj.energy_pump
+(
+  id varchar(32) references tj.pumps(id) not null
+, param tj.energy_param not null
+, value numeric not null
+);
+
+-- demand charge   value
+create table tj.energy_demand_charge
+(
+  value numeric not null
+);
diff --git a/script/script/table/create/16.emitters.sql b/script/script/table/create/16.emitters.sql
new file mode 100644
index 0000000..448b9e1
--- /dev/null
+++ b/script/script/table/create/16.emitters.sql
@@ -0,0 +1,7 @@
+-- [emitters]
+
+create table tj.emitters
+(
+  junction varchar(32) primary key references tj.junctions(id)
+, coefficient numeric not null
+);
diff --git a/script/script/table/create/17.quality.sql b/script/script/table/create/17.quality.sql
new file mode 100644
index 0000000..e972b30
--- /dev/null
+++ b/script/script/table/create/17.quality.sql
@@ -0,0 +1,7 @@
+-- [quality]
+
+create table tj.quality
+(
+  node varchar(32) primary key references tj.node(id)
+, initialqual numeric not null
+);
diff --git a/script/script/table/create/18.sources.sql b/script/script/table/create/18.sources.sql
new file mode 100644
index 0000000..25d480d
--- /dev/null
+++ b/script/script/table/create/18.sources.sql
@@ -0,0 +1,17 @@
+-- [sources]
+
+create type tj.sources_type as enum
+(
+  'concen'
+, 'mass'
+, 'flowpaced'
+, 'setpoint'
+);
+
+create table tj.sources
+(
+  node varchar(32) primary key references tj.node(id)
+, type tj.sources_type not null
+, strength numeric not null
+, timepattern varchar(32) references tj.pattern(id)
+);
diff --git a/script/script/table/create/19.reactions.sql b/script/script/table/create/19.reactions.sql
new file mode 100644
index 0000000..7ddab5d
--- /dev/null
+++ b/script/script/table/create/19.reactions.sql
@@ -0,0 +1,55 @@
+-- [reactions]
+
+create type tj.reactions_order_param as enum
+(
+  'bulk'
+, 'wall'
+, 'tank'
+);
+
+create table tj.reactions_order
+(
+  key tj.reactions_order_param not null
+, value numeric not null
+);
+
+create type tj.reactions_global_param as enum
+(
+  'bulk'
+, 'wall'
+);
+
+create table tj.reactions_global
+(
+  key tj.reactions_global_param not null
+, value numeric not null
+);
+
+create type tj.reactions_pipe_param as enum
+(
+  'bulk'
+, 'wall'
+);
+
+create table tj.reactions_pipe
+(
+  key   tj.reactions_pipe_param not null
+, pipe  varchar(32) references tj.pipes(id) not null
+, value numeric not null
+);
+
+create table tj.reactions_tank
+(
+  tank  varchar(32) references tj.tanks(id) not null
+, value numeric not null
+);
+
+create table tj.reactions_limiting_potential
+(
+  value numeric not null
+);
+
+create table tj.reactions_roughness_correlation
+(
+  value numeric not null
+);
diff --git a/script/script/table/create/2.junctions.sql b/script/script/table/create/2.junctions.sql
new file mode 100644
index 0000000..6397246
--- /dev/null
+++ b/script/script/table/create/2.junctions.sql
@@ -0,0 +1,9 @@
+-- [junctions]
+
+create table tj.junctions
+(
+  id varchar(32) primary key references tj.node(id)
+, elevation numeric not null
+, demand numeric
+, pattern varchar(32) references tj.pattern(id)
+);
diff --git a/script/script/table/create/20.mixing.sql b/script/script/table/create/20.mixing.sql
new file mode 100644
index 0000000..65acf21
--- /dev/null
+++ b/script/script/table/create/20.mixing.sql
@@ -0,0 +1,16 @@
+-- [mixing]
+
+create type tj.mixing_model as enum
+(
+  'mixed'
+, '2comp'
+, 'fifo'
+, 'lifo'
+);
+
+create table tj.mixing
+(
+  tank  varchar(32) primary key references tj.tanks(id)
+, model tj.mixing_model not null
+, value numeric
+);
diff --git a/script/script/table/create/21.times.sql b/script/script/table/create/21.times.sql
new file mode 100644
index 0000000..f66ce2d
--- /dev/null
+++ b/script/script/table/create/21.times.sql
@@ -0,0 +1,9 @@
+-- [times]
+
+-- todo: constraint
+
+create table tj.times
+(
+  key   text not null
+, value text not null
+);
diff --git a/script/script/table/create/22.report.sql b/script/script/table/create/22.report.sql
new file mode 100644
index 0000000..4434a05
--- /dev/null
+++ b/script/script/table/create/22.report.sql
@@ -0,0 +1,9 @@
+-- [report]
+
+-- todo: constraint
+
+create table tj.report
+(
+  key   text not null
+, value text not null
+);
diff --git a/script/script/table/create/23.options.sql b/script/script/table/create/23.options.sql
new file mode 100644
index 0000000..cab34f4
--- /dev/null
+++ b/script/script/table/create/23.options.sql
@@ -0,0 +1,9 @@
+-- [options]
+
+-- todo: constraint
+
+create table tj.options
+(
+  key   text not null
+, value text not null
+);
diff --git a/script/script/table/create/24.coordinates.sql b/script/script/table/create/24.coordinates.sql
new file mode 100644
index 0000000..9b2af3b
--- /dev/null
+++ b/script/script/table/create/24.coordinates.sql
@@ -0,0 +1,10 @@
+-- [coordinates]
+
+create table tj.coordinates
+(
+  node varchar(32) primary key references tj.node(id)
+, coord point not null
+);
+
+create index tj_coordinates_spgist on tj.coordinates using spgist(coord);
+create index tj_coordinates_gist on tj.coordinates using gist(coord);
diff --git a/script/script/table/create/25.vertices.sql b/script/script/table/create/25.vertices.sql
new file mode 100644
index 0000000..7b4d403
--- /dev/null
+++ b/script/script/table/create/25.vertices.sql
@@ -0,0 +1,8 @@
+-- [vertices]
+
+create table tj.vertices
+(
+  link varchar(32) references tj.link(id) not null
+, x    numeric not null
+, y    numeric not null
+);
diff --git a/script/script/table/create/26.labels.sql b/script/script/table/create/26.labels.sql
new file mode 100644
index 0000000..3b41fce
--- /dev/null
+++ b/script/script/table/create/26.labels.sql
@@ -0,0 +1,9 @@
+-- [labels]
+
+create table tj.labels
+(
+  x numeric not null
+, y numeric not null
+, label text not null
+, anchornode varchar(32) references tj.node(id)
+);
diff --git a/script/script/table/create/27.backdrop.sql b/script/script/table/create/27.backdrop.sql
new file mode 100644
index 0000000..aea6d3b
--- /dev/null
+++ b/script/script/table/create/27.backdrop.sql
@@ -0,0 +1,6 @@
+-- [backdrop]
+
+create table tj.backdrop
+(
+  content text primary key
+);
diff --git a/script/sql/section_create/28.end.sql b/script/script/table/create/28.end.sql
similarity index 100%
rename from script/sql/section_create/28.end.sql
rename to script/script/table/create/28.end.sql
diff --git a/script/script/table/create/3.reservoirs.sql b/script/script/table/create/3.reservoirs.sql
new file mode 100644
index 0000000..e7562ec
--- /dev/null
+++ b/script/script/table/create/3.reservoirs.sql
@@ -0,0 +1,8 @@
+-- [reservoirs]
+
+create table tj.reservoirs
+(
+  id varchar(32) primary key references tj.node(id)
+, head numeric not null
+, pattern varchar(32) references tj.pattern(id)
+);
diff --git a/script/script/table/create/4.tanks.sql b/script/script/table/create/4.tanks.sql
new file mode 100644
index 0000000..5a9a815
--- /dev/null
+++ b/script/script/table/create/4.tanks.sql
@@ -0,0 +1,20 @@
+-- [tanks]
+
+create type tj.tanks_overflow as enum
+(
+  'yes'
+, 'no'
+);
+
+create table tj.tanks
+(
+  id varchar(32) primary key references tj.node(id)
+, elevation numeric not null
+, initlevel numeric not null
+, minlevel numeric not null
+, maxlevel numeric not null
+, diameter numeric not null
+, minvol numeric not null
+, volcurve varchar(32) references tj.curve(id)
+, overflow tj.tanks_overflow
+);
diff --git a/script/script/table/create/5.pipes.sql b/script/script/table/create/5.pipes.sql
new file mode 100644
index 0000000..d7ec73e
--- /dev/null
+++ b/script/script/table/create/5.pipes.sql
@@ -0,0 +1,20 @@
+-- [pipes]
+
+create type tj.pipes_status as enum
+(
+  'open'
+, 'closed'
+, 'cv'
+);
+
+create table tj.pipes
+(
+  id varchar(32) primary key references tj.link(id)
+, node1 varchar(32) references tj.node(id) not null
+, node2 varchar(32) references tj.node(id) not null
+, length numeric not null
+, diameter numeric not null
+, roughness numeric not null
+, minorloss numeric not null
+, status tj.pipes_status not null
+);
diff --git a/script/script/table/create/6.pumps.sql b/script/script/table/create/6.pumps.sql
new file mode 100644
index 0000000..0f5b0cf
--- /dev/null
+++ b/script/script/table/create/6.pumps.sql
@@ -0,0 +1,32 @@
+-- [pumps]
+
+create table tj.pumps
+(
+  id varchar(32) primary key references tj.link(id)
+, node1 varchar(32) references tj.node(id) not null
+, node2 varchar(32) references tj.node(id) not null
+);
+
+create table tj.pumps_property_power
+(
+  id varchar primary key references tj.pumps(id)
+, value varchar(32) not null
+);
+
+create table tj.pumps_property_speed
+(
+  id varchar primary key references tj.pumps(id)
+, value varchar(32) not null
+);
+
+create table tj.pumps_property_head
+(
+  id varchar primary key references tj.pumps(id)
+, head varchar(32) references tj.curve(id) not null
+);
+
+create table tj.pumps_property_pattern
+(
+  id varchar primary key references tj.pumps(id)
+, pattern varchar(32) references tj.pattern(id) not null
+);
diff --git a/script/script/table/create/7.valves.sql b/script/script/table/create/7.valves.sql
new file mode 100644
index 0000000..5aa584d
--- /dev/null
+++ b/script/script/table/create/7.valves.sql
@@ -0,0 +1,22 @@
+-- [valves]
+
+create type tj.valves_type as enum
+(
+  'prv'
+, 'psv'
+, 'pbv'
+, 'fcv'
+, 'tcv'
+, 'gpv'
+);
+
+create table tj.valves
+(
+  id varchar(32) primary key references tj.link(id)
+, node1 varchar(32) references tj.node(id) not null
+, node2 varchar(32) references tj.node(id) not null
+, diameter numeric not null
+, type tj.valves_type not null
+, setting numeric not null
+, minorloss numeric not null
+);
diff --git a/script/script/table/create/8.tags.sql b/script/script/table/create/8.tags.sql
new file mode 100644
index 0000000..d98132c
--- /dev/null
+++ b/script/script/table/create/8.tags.sql
@@ -0,0 +1,13 @@
+-- [tags]
+
+create table tj.tags_node
+(
+  id varchar(32) primary key references tj.node(id)
+, tag text not null
+);
+
+create table tj.tags_link
+(
+  id varchar(32) primary key references tj.link(id)
+, tag text not null
+);
diff --git a/script/script/table/create/9.demands.sql b/script/script/table/create/9.demands.sql
new file mode 100644
index 0000000..e908227
--- /dev/null
+++ b/script/script/table/create/9.demands.sql
@@ -0,0 +1,9 @@
+-- [demands]
+
+create table tj.demands
+(
+  junction varchar(32) references tj.junctions(id) not null
+, demand numeric not null
+, pattern varchar(32) references tj.pattern(id)
+, category text not null
+);
diff --git a/script/script/table/create/namespace.sql b/script/script/table/create/namespace.sql
new file mode 100644
index 0000000..fc993ed
--- /dev/null
+++ b/script/script/table/create/namespace.sql
@@ -0,0 +1 @@
+create schema tj;
\ No newline at end of file
diff --git a/script/script/table/create/operation.sql b/script/script/table/create/operation.sql
new file mode 100644
index 0000000..524ef9e
--- /dev/null
+++ b/script/script/table/create/operation.sql
@@ -0,0 +1,29 @@
+create table tj.operation
+(
+  id serial primary key
+, redo text not null
+, undo text not null
+, parent integer references tj.operation(id)
+, redo_child integer references tj.operation(id)
+);
+
+insert into tj.operation (id, redo, undo) values (0, '', '');
+
+create table tj.current_operation
+(
+  id integer primary key references tj.operation(id)
+);
+
+insert into tj.current_operation (id) values (0);
+
+create table tj.snapshot_operation
+(
+  id integer primary key references tj.operation(id)
+, tag text not null unique
+);
+
+create table tj.transaction_operation
+(
+  id integer primary key references tj.operation(id)
+, strict boolean not null default false
+);
diff --git a/script/script/table/drop/0.base.sql b/script/script/table/drop/0.base.sql
new file mode 100644
index 0000000..41c4f41
--- /dev/null
+++ b/script/script/table/drop/0.base.sql
@@ -0,0 +1,11 @@
+drop table if exists tj.pattern;
+
+drop table if exists tj.curve;
+
+drop table if exists tj.link;
+
+drop table if exists tj.node;
+
+drop type if exists tj.link_type;
+
+drop type if exists tj.node_type;
diff --git a/script/script/table/drop/1.title.sql b/script/script/table/drop/1.title.sql
new file mode 100644
index 0000000..a03e80a
--- /dev/null
+++ b/script/script/table/drop/1.title.sql
@@ -0,0 +1,3 @@
+-- [title]
+
+drop table if exists tj.title;
diff --git a/script/script/table/drop/10.status.sql b/script/script/table/drop/10.status.sql
new file mode 100644
index 0000000..232ca4d
--- /dev/null
+++ b/script/script/table/drop/10.status.sql
@@ -0,0 +1,13 @@
+-- [status]
+
+drop table if exists tj.status_link;
+
+drop table if exists tj.status_valve;
+
+drop type if exists tj.status_valve_status;
+
+drop table if exists tj.status_pump;
+
+drop table if exists tj.status_pipe;
+
+drop type if exists tj.status_pipe_pump_status;
diff --git a/script/script/table/drop/11.patterns.sql b/script/script/table/drop/11.patterns.sql
new file mode 100644
index 0000000..5fb2b47
--- /dev/null
+++ b/script/script/table/drop/11.patterns.sql
@@ -0,0 +1,3 @@
+-- [patterns]
+
+drop table if exists tj.patterns;
diff --git a/script/script/table/drop/12.curves.sql b/script/script/table/drop/12.curves.sql
new file mode 100644
index 0000000..4874ee8
--- /dev/null
+++ b/script/script/table/drop/12.curves.sql
@@ -0,0 +1,3 @@
+-- [curves]
+
+drop table if exists tj.curves;
diff --git a/script/script/table/drop/13.controls.sql b/script/script/table/drop/13.controls.sql
new file mode 100644
index 0000000..f6c0502
--- /dev/null
+++ b/script/script/table/drop/13.controls.sql
@@ -0,0 +1,9 @@
+-- [controls]
+
+drop table if exists tj.controls_3;
+
+drop table if exists tj.controls_2;
+
+drop table if exists tj.controls_1;
+
+drop type if exists tj.controls_1_prep;
diff --git a/script/script/table/drop/14.rules.sql b/script/script/table/drop/14.rules.sql
new file mode 100644
index 0000000..a920e6a
--- /dev/null
+++ b/script/script/table/drop/14.rules.sql
@@ -0,0 +1,3 @@
+-- [rules]
+
+drop table if exists tj.rules;
diff --git a/script/script/table/drop/15.energy.sql b/script/script/table/drop/15.energy.sql
new file mode 100644
index 0000000..abf2e4a
--- /dev/null
+++ b/script/script/table/drop/15.energy.sql
@@ -0,0 +1,9 @@
+-- [energy]
+
+drop table if exists tj.energy_demand_charge;
+
+drop table if exists tj.energy_pump;
+
+drop table if exists tj.energy_global;
+
+drop type if exists tj.energy_param;
diff --git a/script/script/table/drop/16.emitters.sql b/script/script/table/drop/16.emitters.sql
new file mode 100644
index 0000000..ec23cd3
--- /dev/null
+++ b/script/script/table/drop/16.emitters.sql
@@ -0,0 +1,3 @@
+-- [emitters]
+
+drop table if exists tj.emitters;
diff --git a/script/script/table/drop/17.quality.sql b/script/script/table/drop/17.quality.sql
new file mode 100644
index 0000000..673cd2f
--- /dev/null
+++ b/script/script/table/drop/17.quality.sql
@@ -0,0 +1,3 @@
+-- [quality]
+
+drop table if exists tj.quality;
diff --git a/script/script/table/drop/18.sources.sql b/script/script/table/drop/18.sources.sql
new file mode 100644
index 0000000..e9487c8
--- /dev/null
+++ b/script/script/table/drop/18.sources.sql
@@ -0,0 +1,5 @@
+-- [sources]
+
+drop table if exists tj.sources;
+
+drop type if exists tj.sources_type;
diff --git a/script/script/table/drop/19.reactions.sql b/script/script/table/drop/19.reactions.sql
new file mode 100644
index 0000000..0dff3f0
--- /dev/null
+++ b/script/script/table/drop/19.reactions.sql
@@ -0,0 +1,19 @@
+-- [reactions]
+
+drop table if exists tj.reactions_roughness_correlation;
+
+drop table if exists tj.reactions_limiting_potential;
+
+drop table if exists tj.reactions_tank;
+
+drop table if exists tj.reactions_pipe;
+
+drop type if exists tj.reactions_pipe_param;
+
+drop table if exists tj.reactions_global;
+
+drop type if exists tj.reactions_global_param;
+
+drop table if exists tj.reactions_order;
+
+drop type if exists tj.reactions_order_param;
diff --git a/script/script/table/drop/2.junctions.sql b/script/script/table/drop/2.junctions.sql
new file mode 100644
index 0000000..0b436c4
--- /dev/null
+++ b/script/script/table/drop/2.junctions.sql
@@ -0,0 +1,3 @@
+-- [junctions]
+
+drop table if exists tj.junctions;
diff --git a/script/script/table/drop/20.mixing.sql b/script/script/table/drop/20.mixing.sql
new file mode 100644
index 0000000..f2adc25
--- /dev/null
+++ b/script/script/table/drop/20.mixing.sql
@@ -0,0 +1,5 @@
+-- [mixing]
+
+drop table if exists tj.mixing;
+
+drop type if exists tj.mixing_model;
diff --git a/script/script/table/drop/21.times.sql b/script/script/table/drop/21.times.sql
new file mode 100644
index 0000000..b56a5cf
--- /dev/null
+++ b/script/script/table/drop/21.times.sql
@@ -0,0 +1,3 @@
+-- [times]
+
+drop table if exists tj.times;
diff --git a/script/script/table/drop/22.report.sql b/script/script/table/drop/22.report.sql
new file mode 100644
index 0000000..03f771b
--- /dev/null
+++ b/script/script/table/drop/22.report.sql
@@ -0,0 +1,3 @@
+-- [report]
+
+drop table if exists tj.report;
diff --git a/script/script/table/drop/23.options.sql b/script/script/table/drop/23.options.sql
new file mode 100644
index 0000000..dc8c63c
--- /dev/null
+++ b/script/script/table/drop/23.options.sql
@@ -0,0 +1,3 @@
+-- [options]
+
+drop table if exists tj.options;
diff --git a/script/script/table/drop/24.coordinates.sql b/script/script/table/drop/24.coordinates.sql
new file mode 100644
index 0000000..0d74d3e
--- /dev/null
+++ b/script/script/table/drop/24.coordinates.sql
@@ -0,0 +1,7 @@
+-- [coordinates]
+
+drop index if exists tj_coordinates_gist;
+
+drop index if exists tj_coordinates_spgist;
+
+drop table if exists tj.coordinates;
diff --git a/script/script/table/drop/25.vertices.sql b/script/script/table/drop/25.vertices.sql
new file mode 100644
index 0000000..a060c4a
--- /dev/null
+++ b/script/script/table/drop/25.vertices.sql
@@ -0,0 +1,3 @@
+-- [vertices]
+
+drop table if exists tj.vertices;
diff --git a/script/script/table/drop/26.labels.sql b/script/script/table/drop/26.labels.sql
new file mode 100644
index 0000000..4f9f743
--- /dev/null
+++ b/script/script/table/drop/26.labels.sql
@@ -0,0 +1,3 @@
+-- [labels]
+
+drop table if exists tj.labels;
diff --git a/script/script/table/drop/27.backdrop.sql b/script/script/table/drop/27.backdrop.sql
new file mode 100644
index 0000000..ba47de7
--- /dev/null
+++ b/script/script/table/drop/27.backdrop.sql
@@ -0,0 +1,3 @@
+-- [backdrop]
+
+drop table if exists tj.backdrop;
diff --git a/script/sql/section_drop/28.end.sql b/script/script/table/drop/28.end.sql
similarity index 100%
rename from script/sql/section_drop/28.end.sql
rename to script/script/table/drop/28.end.sql
diff --git a/script/script/table/drop/3.reservoirs.sql b/script/script/table/drop/3.reservoirs.sql
new file mode 100644
index 0000000..c9a1e25
--- /dev/null
+++ b/script/script/table/drop/3.reservoirs.sql
@@ -0,0 +1,3 @@
+-- [reservoirs]
+
+drop table if exists tj.reservoirs;
diff --git a/script/script/table/drop/4.tanks.sql b/script/script/table/drop/4.tanks.sql
new file mode 100644
index 0000000..0a5e589
--- /dev/null
+++ b/script/script/table/drop/4.tanks.sql
@@ -0,0 +1,5 @@
+-- [tanks]
+
+drop table if exists tj.tanks;
+
+drop type if exists tj.tanks_overflow;
diff --git a/script/script/table/drop/5.pipes.sql b/script/script/table/drop/5.pipes.sql
new file mode 100644
index 0000000..0cdc8dc
--- /dev/null
+++ b/script/script/table/drop/5.pipes.sql
@@ -0,0 +1,5 @@
+-- [pipes]
+
+drop table if exists tj.pipes;
+
+drop type if exists tj.pipes_status;
diff --git a/script/script/table/drop/6.pumps.sql b/script/script/table/drop/6.pumps.sql
new file mode 100644
index 0000000..18d697b
--- /dev/null
+++ b/script/script/table/drop/6.pumps.sql
@@ -0,0 +1,11 @@
+-- [pumps]
+
+drop table if exists tj.pumps_property_pattern;
+
+drop table if exists tj.pumps_property_head;
+
+drop table if exists tj.pumps_property_speed;
+
+drop table if exists tj.pumps_property_power;
+
+drop table if exists tj.pumps;
diff --git a/script/script/table/drop/7.valves.sql b/script/script/table/drop/7.valves.sql
new file mode 100644
index 0000000..0c2c2d1
--- /dev/null
+++ b/script/script/table/drop/7.valves.sql
@@ -0,0 +1,5 @@
+-- [valves]
+
+drop table if exists tj.valves;
+
+drop type if exists tj.valves_type;
diff --git a/script/script/table/drop/8.tags.sql b/script/script/table/drop/8.tags.sql
new file mode 100644
index 0000000..e277759
--- /dev/null
+++ b/script/script/table/drop/8.tags.sql
@@ -0,0 +1,5 @@
+-- [tags]
+
+drop table if exists tj.tags_link;
+
+drop table if exists tj.tags_node;
diff --git a/script/script/table/drop/9.demands.sql b/script/script/table/drop/9.demands.sql
new file mode 100644
index 0000000..8478a8b
--- /dev/null
+++ b/script/script/table/drop/9.demands.sql
@@ -0,0 +1,3 @@
+-- [demands]
+
+drop table if exists tj.demands;
diff --git a/script/script/table/drop/namespace.sql b/script/script/table/drop/namespace.sql
new file mode 100644
index 0000000..effb087
--- /dev/null
+++ b/script/script/table/drop/namespace.sql
@@ -0,0 +1 @@
+drop schema if exists tj;
\ No newline at end of file
diff --git a/script/script/table/drop/operation.sql b/script/script/table/drop/operation.sql
new file mode 100644
index 0000000..cf3dc7b
--- /dev/null
+++ b/script/script/table/drop/operation.sql
@@ -0,0 +1,7 @@
+drop table if exists tj.transaction_operation;
+
+drop table if exists tj.snapshot_operation;
+
+drop table if exists tj.current_operation;
+
+drop table if exists tj.operation;
diff --git a/script/script/template.py b/script/script/template.py
new file mode 100644
index 0000000..7ed9a98
--- /dev/null
+++ b/script/script/template.py
@@ -0,0 +1,108 @@
+import psycopg as pg
+
+sql_create = [
+    "table/create/namespace.sql",
+    "table/create/0.base.sql",
+    "table/create/1.title.sql",
+    "table/create/2.junctions.sql",
+    "table/create/3.reservoirs.sql",
+    "table/create/4.tanks.sql",
+    "table/create/5.pipes.sql",
+    "table/create/6.pumps.sql",
+    "table/create/7.valves.sql",
+    "table/create/8.tags.sql",
+    "table/create/9.demands.sql",
+    "table/create/10.status.sql",
+    "table/create/11.patterns.sql",
+    "table/create/12.curves.sql",
+    "table/create/13.controls.sql",
+    "table/create/14.rules.sql",
+    "table/create/15.energy.sql",
+    "table/create/16.emitters.sql",
+    "table/create/17.quality.sql",
+    "table/create/18.sources.sql",
+    "table/create/19.reactions.sql",
+    "table/create/20.mixing.sql",
+    "table/create/21.times.sql",
+    "table/create/22.report.sql",
+    "table/create/23.options.sql",
+    "table/create/24.coordinates.sql",
+    "table/create/25.vertices.sql",
+    "table/create/26.labels.sql",
+    "table/create/27.backdrop.sql",
+    "table/create/28.end.sql",
+    "table/create/operation.sql",
+    "api/create/operation.sql",
+    "api/create/1.title.sql"
+]
+
+sql_drop = [
+    "api/drop/1.title.sql",
+    "api/drop/operation.sql",
+    "table/drop/operation.sql",
+    "table/drop/28.end.sql",
+    "table/drop/27.backdrop.sql",
+    "table/drop/26.labels.sql",
+    "table/drop/25.vertices.sql",
+    "table/drop/24.coordinates.sql",
+    "table/drop/23.options.sql",
+    "table/drop/22.report.sql",
+    "table/drop/21.times.sql",
+    "table/drop/20.mixing.sql",
+    "table/drop/19.reactions.sql",
+    "table/drop/18.sources.sql",
+    "table/drop/17.quality.sql",
+    "table/drop/16.emitters.sql",
+    "table/drop/15.energy.sql",
+    "table/drop/14.rules.sql",
+    "table/drop/13.controls.sql",
+    "table/drop/12.curves.sql",
+    "table/drop/11.patterns.sql",
+    "table/drop/10.status.sql",
+    "table/drop/9.demands.sql",
+    "table/drop/8.tags.sql",
+    "table/drop/7.valves.sql",
+    "table/drop/6.pumps.sql",
+    "table/drop/5.pipes.sql",
+    "table/drop/4.tanks.sql",
+    "table/drop/3.reservoirs.sql",
+    "table/drop/2.junctions.sql",
+    "table/drop/1.title.sql",
+    "table/drop/0.base.sql",
+    "table/drop/namespace.sql"
+]
+
+def create_template():
+    with pg.connect(conninfo="dbname=postgres", autocommit=True) as conn:
+        with conn.cursor() as cur:
+            cur.execute("create database tj_project")
+    with pg.connect(conninfo="dbname=tj_project") as conn:
+        with conn.cursor() as cur:
+            for sql in sql_create:
+                with open(sql, "r") as f:
+                    cur.execute(f.read())
+                print(f'executed {sql}')
+        conn.commit()
+
+def have_template():
+    with pg.connect(conninfo="dbname=postgres", autocommit=True) as conn:
+        with conn.cursor() as cur:
+            cur.execute("select * from pg_database where datname = 'tj_project'")
+            return cur.rowcount > 0
+
+def delete_template():
+    with pg.connect(conninfo="dbname=tj_project") as conn:
+        with conn.cursor() as cur:
+            for sql in sql_drop:
+                with open(sql, "r") as f:
+                    cur.execute(f.read())
+                print(f'executed {sql}')
+        conn.commit()
+    with pg.connect(conninfo="dbname=postgres", autocommit=True) as conn:
+        with conn.cursor() as cur:
+            cur.execute("drop database tj_project")
+
+if __name__ == "__main__":
+    if (have_template()):
+        delete_template()
+    create_template()
diff --git a/script/sql/base_create.sql b/script/sql/create/0.base.sql
similarity index 100%
rename from script/sql/base_create.sql
rename to script/sql/create/0.base.sql
diff --git a/script/sql/section_create/1.title.sql b/script/sql/create/1.title.sql
similarity index 55%
rename from script/sql/section_create/1.title.sql
rename to script/sql/create/1.title.sql
index 0a48eff..c00e981 100644
--- a/script/sql/section_create/1.title.sql
+++ b/script/sql/create/1.title.sql
@@ -4,3 +4,5 @@ CREATE TABLE TITLE
 (
   Value TEXT
 );
+
+INSERT INTO TITLE (Value) VALUES ('');
diff --git a/script/sql/section_create/10.status.sql b/script/sql/create/10.status.sql
similarity index 100%
rename from script/sql/section_create/10.status.sql
rename to script/sql/create/10.status.sql
diff --git a/script/sql/section_create/11.patterns.sql b/script/sql/create/11.patterns.sql
similarity index 100%
rename from script/sql/section_create/11.patterns.sql
rename to script/sql/create/11.patterns.sql
diff --git a/script/sql/section_create/12.curves.sql b/script/sql/create/12.curves.sql
similarity index 100%
rename from script/sql/section_create/12.curves.sql
rename to script/sql/create/12.curves.sql
diff --git a/script/sql/section_create/13.controls.sql b/script/sql/create/13.controls.sql
similarity index 100%
rename from script/sql/section_create/13.controls.sql
rename to script/sql/create/13.controls.sql
diff --git a/script/sql/section_create/14.rules.sql b/script/sql/create/14.rules.sql
similarity index 100%
rename from script/sql/section_create/14.rules.sql
rename to script/sql/create/14.rules.sql
diff --git a/script/sql/section_create/15.energy.sql b/script/sql/create/15.energy.sql
similarity index 100%
rename from script/sql/section_create/15.energy.sql
rename to script/sql/create/15.energy.sql
diff --git a/script/sql/section_create/16.emitters.sql b/script/sql/create/16.emitters.sql
similarity index 100%
rename from script/sql/section_create/16.emitters.sql
rename to script/sql/create/16.emitters.sql
diff --git a/script/sql/section_create/17.quality.sql b/script/sql/create/17.quality.sql
similarity index 100%
rename from script/sql/section_create/17.quality.sql
rename to script/sql/create/17.quality.sql
diff --git a/script/sql/section_create/18.sources.sql b/script/sql/create/18.sources.sql
similarity index 100%
rename from script/sql/section_create/18.sources.sql
rename to script/sql/create/18.sources.sql
diff --git a/script/sql/section_create/19.reactions.sql b/script/sql/create/19.reactions.sql
similarity index 100%
rename from script/sql/section_create/19.reactions.sql
rename to script/sql/create/19.reactions.sql
diff --git a/script/sql/section_create/2.junctions.sql b/script/sql/create/2.junctions.sql
similarity index 100%
rename from script/sql/section_create/2.junctions.sql
rename to script/sql/create/2.junctions.sql
diff --git a/script/sql/section_create/20.mixing.sql b/script/sql/create/20.mixing.sql
similarity index 100%
rename from script/sql/section_create/20.mixing.sql
rename to script/sql/create/20.mixing.sql
diff --git a/script/sql/section_create/21.times.sql b/script/sql/create/21.times.sql
similarity index 100%
rename from script/sql/section_create/21.times.sql
rename to script/sql/create/21.times.sql
diff --git a/script/sql/section_create/22.report.sql b/script/sql/create/22.report.sql
similarity index 100%
rename from script/sql/section_create/22.report.sql
rename to script/sql/create/22.report.sql
diff --git a/script/sql/section_create/23.options.sql b/script/sql/create/23.options.sql
similarity index 100%
rename from script/sql/section_create/23.options.sql
rename to script/sql/create/23.options.sql
diff --git a/script/sql/section_create/24.coordinates.sql b/script/sql/create/24.coordinates.sql
similarity index 82%
rename from script/sql/section_create/24.coordinates.sql
rename to script/sql/create/24.coordinates.sql
index 2bad5dc..5b6ed6d 100644
--- a/script/sql/section_create/24.coordinates.sql
+++ b/script/sql/create/24.coordinates.sql
@@ -3,7 +3,7 @@
 CREATE TABLE COORDINATES
 (
   Node VARCHAR(32) PRIMARY KEY REFERENCES _NODE(ID)
-, Coord POINT NOT NULL DEFAULT(POINT(0.0, 0.0))
+, Coord POINT NOT NULL
 );
 
 CREATE INDEX COORDINATES_SPGIST ON COORDINATES USING SPGIST(Coord);
diff --git a/script/sql/section_create/25.vertices.sql b/script/sql/create/25.vertices.sql
similarity index 100%
rename from script/sql/section_create/25.vertices.sql
rename to script/sql/create/25.vertices.sql
diff --git a/script/sql/section_create/26.labels.sql b/script/sql/create/26.labels.sql
similarity index 100%
rename from script/sql/section_create/26.labels.sql
rename to script/sql/create/26.labels.sql
diff --git a/script/sql/section_create/27.backdrop.sql b/script/sql/create/27.backdrop.sql
similarity index 100%
rename from script/sql/section_create/27.backdrop.sql
rename to script/sql/create/27.backdrop.sql
diff --git a/script/sql/create/28.end.sql b/script/sql/create/28.end.sql
new file mode 100644
index 0000000..3054ad0
--- /dev/null
+++ b/script/sql/create/28.end.sql
@@ -0,0 +1 @@
+-- [END]
\ No newline at end of file
diff --git a/script/sql/section_create/3.reservoirs.sql b/script/sql/create/3.reservoirs.sql
similarity index 100%
rename from script/sql/section_create/3.reservoirs.sql
rename to script/sql/create/3.reservoirs.sql
diff --git a/script/sql/section_create/4.tanks.sql b/script/sql/create/4.tanks.sql
similarity index 100%
rename from script/sql/section_create/4.tanks.sql
rename to script/sql/create/4.tanks.sql
diff --git a/script/sql/section_create/5.pipes.sql b/script/sql/create/5.pipes.sql
similarity index 100%
rename from script/sql/section_create/5.pipes.sql
rename to script/sql/create/5.pipes.sql
diff --git a/script/sql/section_create/6.pumps.sql b/script/sql/create/6.pumps.sql
similarity index 100%
rename from script/sql/section_create/6.pumps.sql
rename to script/sql/create/6.pumps.sql
diff --git a/script/sql/section_create/7.valves.sql b/script/sql/create/7.valves.sql
similarity index 100%
rename from script/sql/section_create/7.valves.sql
rename to script/sql/create/7.valves.sql
diff --git a/script/sql/section_create/8.tags.sql b/script/sql/create/8.tags.sql
similarity index 100%
rename from script/sql/section_create/8.tags.sql
rename to script/sql/create/8.tags.sql
diff --git a/script/sql/section_create/9.demands.sql b/script/sql/create/9.demands.sql
similarity index 100%
rename from script/sql/section_create/9.demands.sql
rename to script/sql/create/9.demands.sql
diff --git a/script/sql/create/operation.sql b/script/sql/create/operation.sql
new file mode 100644
index 0000000..2f105e6
--- /dev/null
+++ b/script/sql/create/operation.sql
@@ -0,0 +1,29 @@
+CREATE TABLE OPERATION
+(
+  ID SERIAL PRIMARY KEY
+, Redo TEXT NOT NULL
+, Undo TEXT NOT NULL
+, Parent INTEGER REFERENCES OPERATION(ID)
+, Redo_Child INTEGER REFERENCES OPERATION(ID)
+);
+
+INSERT INTO OPERATION (ID, Redo, Undo) VALUES (0, '', '');
+
+CREATE TABLE CURRENT_OPERATION
+(
+  ID INTEGER PRIMARY KEY REFERENCES OPERATION(ID)
+);
+
+INSERT INTO CURRENT_OPERATION (ID) VALUES (0);
+
+CREATE TABLE SNAPSHOT_OPERATION
+(
+  ID INTEGER PRIMARY KEY REFERENCES OPERATION(ID)
+, Tag TEXT NOT NULL UNIQUE
+);
+
+CREATE TABLE TRANSACTION_OPERATION
+(
+  ID INTEGER PRIMARY KEY REFERENCES OPERATION(ID)
+, STRICT BOOLEAN NOT NULL DEFAULT FALSE
+);
diff --git a/script/sql/base_drop.sql b/script/sql/drop/0.base.sql
similarity index 100%
rename from script/sql/base_drop.sql
rename to script/sql/drop/0.base.sql
diff --git a/script/sql/drop/1.title.sql b/script/sql/drop/1.title.sql
new file mode 100644
index 0000000..7ee6d55
--- /dev/null
+++ b/script/sql/drop/1.title.sql
@@ -0,0 +1,3 @@
+-- [TITLE]
+
+DROP TABLE IF EXISTS TITLE;
diff --git a/script/sql/drop/10.status.sql b/script/sql/drop/10.status.sql
new file mode 100644
index 0000000..322a72f
--- /dev/null
+++ b/script/sql/drop/10.status.sql
@@ -0,0 +1,13 @@
+-- [STATUS]
+
+DROP TABLE IF EXISTS STATUS_LINK;
+
+DROP TABLE IF EXISTS STATUS_VALVE;
+
+DROP TYPE IF EXISTS STATUS_VALVE_STATUS;
+
+DROP TABLE IF EXISTS STATUS_PUMP;
+
+DROP TABLE IF EXISTS STATUS_PIPE;
+
+DROP TYPE IF EXISTS STATUS_PIPE_PUMP_STATUS;
diff --git a/script/sql/drop/11.patterns.sql b/script/sql/drop/11.patterns.sql
new file mode 100644
index 0000000..fd08d97
--- /dev/null
+++ b/script/sql/drop/11.patterns.sql
@@ -0,0 +1,3 @@
+-- [PATTERNS]
+
+DROP TABLE IF EXISTS PATTERNS;
diff --git a/script/sql/drop/12.curves.sql b/script/sql/drop/12.curves.sql
new file mode 100644
index 0000000..577464e
--- /dev/null
+++ b/script/sql/drop/12.curves.sql
@@ -0,0 +1,3 @@
+-- [CURVES]
+
+DROP TABLE IF EXISTS CURVES;
diff --git a/script/sql/drop/13.controls.sql b/script/sql/drop/13.controls.sql
new file mode 100644
index 0000000..476259d
--- /dev/null
+++ b/script/sql/drop/13.controls.sql
@@ -0,0 +1,9 @@
+-- [CONTROLS]
+
+DROP TABLE IF EXISTS CONTROLS_3;
+
+DROP TABLE IF EXISTS CONTROLS_2;
+
+DROP TABLE IF EXISTS CONTROLS_1;
+
+DROP TYPE IF EXISTS CONTROLS_1_PREP;
diff --git a/script/sql/drop/14.rules.sql b/script/sql/drop/14.rules.sql
new file mode 100644
index 0000000..84e4fd8
--- /dev/null
+++ b/script/sql/drop/14.rules.sql
@@ -0,0 +1,3 @@
+-- [RULES]
+
+DROP TABLE IF EXISTS RULES;
diff --git a/script/sql/drop/15.energy.sql b/script/sql/drop/15.energy.sql
new file mode 100644
index 0000000..5002d5c
--- /dev/null
+++ b/script/sql/drop/15.energy.sql
@@ -0,0 +1,9 @@
+-- [ENERGY]
+
+DROP TABLE IF EXISTS ENERGY_DEMAND_CHARGE;
+
+DROP TABLE IF EXISTS ENERGY_PUMP;
+
+DROP TABLE IF EXISTS ENERGY_GLOBAL;
+
+DROP TYPE IF EXISTS ENERGY_PARAM;
diff --git a/script/sql/drop/16.emitters.sql b/script/sql/drop/16.emitters.sql
new file mode 100644
index 0000000..40a0af8
--- /dev/null
+++ b/script/sql/drop/16.emitters.sql
@@ -0,0 +1,3 @@
+-- [EMITTERS]
+
+DROP TABLE IF EXISTS EMITTERS;
diff --git a/script/sql/drop/17.quality.sql b/script/sql/drop/17.quality.sql
new file mode 100644
index 0000000..b72c290
--- /dev/null
+++ b/script/sql/drop/17.quality.sql
@@ -0,0 +1,3 @@
+-- [QUALITY]
+
+DROP TABLE IF EXISTS QUALITY;
diff --git a/script/sql/drop/18.sources.sql b/script/sql/drop/18.sources.sql
new file mode 100644
index 0000000..0402ffe
--- /dev/null
+++ b/script/sql/drop/18.sources.sql
@@ -0,0 +1,5 @@
+-- [SOURCES]
+
+DROP TABLE IF EXISTS SOURCES;
+
+DROP TYPE IF EXISTS SOURCES_TYPE;
diff --git a/script/sql/drop/19.reactions.sql b/script/sql/drop/19.reactions.sql
new file mode 100644
index 0000000..2f6ba5b
--- /dev/null
+++ b/script/sql/drop/19.reactions.sql
@@ -0,0 +1,19 @@
+-- [REACTIONS]
+
+DROP TABLE IF EXISTS REACTIONS_ROUGHNESS_CORRELATION;
+
+DROP TABLE IF EXISTS REACTIONS_LIMITING_POTENTIAL;
+
+DROP TABLE IF EXISTS REACTIONS_TANK;
+
+DROP TABLE IF EXISTS REACTIONS_PIPE;
+
+DROP TYPE IF EXISTS REACTIONS_PIPE_PARAM;
+
+DROP TABLE IF EXISTS REACTIONS_GLOBAL;
+
+DROP TYPE IF EXISTS REACTIONS_GLOBAL_PARAM;
+
+DROP TABLE IF EXISTS REACTIONS_ORDER;
+
+DROP TYPE IF EXISTS REACTIONS_ORDER_PARAM;
diff --git a/script/sql/drop/2.junctions.sql b/script/sql/drop/2.junctions.sql
new file mode 100644
index 0000000..ef0a609
--- /dev/null
+++ b/script/sql/drop/2.junctions.sql
@@ -0,0 +1,3 @@
+-- [JUNCTIONS]
+
+DROP TABLE IF EXISTS JUNCTIONS;
diff --git a/script/sql/drop/20.mixing.sql b/script/sql/drop/20.mixing.sql
new file mode 100644
index 0000000..938d554
--- /dev/null
+++ b/script/sql/drop/20.mixing.sql
@@ -0,0 +1,5 @@
+-- [MIXING]
+
+DROP TABLE IF EXISTS MIXING;
+
+DROP TYPE IF EXISTS MIXING_Model;
diff --git a/script/sql/drop/21.times.sql b/script/sql/drop/21.times.sql
new file mode 100644
index 0000000..f051bd7
--- /dev/null
+++ b/script/sql/drop/21.times.sql
@@ -0,0 +1,3 @@
+-- [TIMES]
+
+DROP TABLE IF EXISTS TIMES;
diff --git a/script/sql/drop/22.report.sql b/script/sql/drop/22.report.sql
new file mode 100644
index 0000000..790684d
--- /dev/null
+++ b/script/sql/drop/22.report.sql
@@ -0,0 +1,3 @@
+-- [REPORT]
+
+DROP TABLE IF EXISTS REPORT;
diff --git a/script/sql/drop/23.options.sql b/script/sql/drop/23.options.sql
new file mode 100644
index 0000000..7cc629a
--- /dev/null
+++ b/script/sql/drop/23.options.sql
@@ -0,0 +1,3 @@
+-- [OPTIONS]
+
+DROP TABLE IF EXISTS OPTIONS;
diff --git a/script/sql/drop/24.coordinates.sql b/script/sql/drop/24.coordinates.sql
new file mode 100644
index 0000000..04d0465
--- /dev/null
+++ b/script/sql/drop/24.coordinates.sql
@@ -0,0 +1,7 @@
+-- [COORDINATES]
+
+DROP INDEX IF EXISTS COORDINATES_GIST;
+
+DROP INDEX IF EXISTS COORDINATES_SPGIST;
+
+DROP TABLE IF EXISTS COORDINATES;
diff --git a/script/sql/drop/25.vertices.sql b/script/sql/drop/25.vertices.sql
new file mode 100644
index 0000000..f74dd3e
--- /dev/null
+++ b/script/sql/drop/25.vertices.sql
@@ -0,0 +1,3 @@
+-- [VERTICES]
+
+DROP TABLE IF EXISTS VERTICES;
diff --git a/script/sql/drop/26.labels.sql b/script/sql/drop/26.labels.sql
new file mode 100644
index 0000000..aa1b2b2
--- /dev/null
+++ b/script/sql/drop/26.labels.sql
@@ -0,0 +1,3 @@
+-- [LABELS]
+
+DROP TABLE IF EXISTS LABELS;
diff --git a/script/sql/drop/27.backdrop.sql b/script/sql/drop/27.backdrop.sql
new file mode 100644
index 0000000..408bb85
--- /dev/null
+++ b/script/sql/drop/27.backdrop.sql
@@ -0,0 +1,3 @@
+-- [BACKDROP]
+
+DROP TABLE IF EXISTS BACKDROP;
diff --git a/script/sql/drop/28.end.sql b/script/sql/drop/28.end.sql
new file mode 100644
index 0000000..3054ad0
--- /dev/null
+++ b/script/sql/drop/28.end.sql
@@ -0,0 +1 @@
+-- [END]
\ No newline at end of file
diff --git a/script/sql/drop/3.reservoirs.sql b/script/sql/drop/3.reservoirs.sql
new file mode 100644
index 0000000..9864c18
--- /dev/null
+++ b/script/sql/drop/3.reservoirs.sql
@@ -0,0 +1,3 @@
+-- [RESERVOIRS]
+
+DROP TABLE IF EXISTS RESERVOIRS;
diff --git a/script/sql/drop/4.tanks.sql b/script/sql/drop/4.tanks.sql
new file mode 100644
index 0000000..da0487d
--- /dev/null
+++ b/script/sql/drop/4.tanks.sql
@@ -0,0 +1,5 @@
+-- [TANKS]
+
+DROP TABLE IF EXISTS TANKS;
+
+DROP TYPE IF EXISTS TANKS_OVERFLOW;
diff --git a/script/sql/drop/5.pipes.sql b/script/sql/drop/5.pipes.sql
new file mode 100644
index 0000000..1e23612
--- /dev/null
+++ b/script/sql/drop/5.pipes.sql
@@ -0,0 +1,5 @@
+-- [PIPES]
+
+DROP TABLE IF EXISTS PIPES;
+
+DROP TYPE IF EXISTS PIPES_STATUS;
diff --git a/script/sql/drop/6.pumps.sql b/script/sql/drop/6.pumps.sql
new file mode 100644
index 0000000..5ac9656
--- /dev/null
+++ b/script/sql/drop/6.pumps.sql
@@ -0,0 +1,11 @@
+-- [PUMPS]
+
+DROP TABLE IF EXISTS PUMPS_PROPERTY_PATTERN;
+
+DROP TABLE IF EXISTS PUMPS_PROPERTY_HEAD;
+
+DROP TABLE IF EXISTS PUMPS_PROPERTY_SPEED;
+
+DROP TABLE IF EXISTS PUMPS_PROPERTY_POWER;
+
+DROP TABLE IF EXISTS PUMPS;
diff --git a/script/sql/drop/7.valves.sql b/script/sql/drop/7.valves.sql
new file mode 100644
index 0000000..c95b423
--- /dev/null
+++ b/script/sql/drop/7.valves.sql
@@ -0,0 +1,5 @@
+-- [VALVES]
+
+DROP TABLE IF EXISTS VALVES;
+
+DROP TYPE IF EXISTS VALVES_TYPE;
diff --git a/script/sql/drop/8.tags.sql b/script/sql/drop/8.tags.sql
new file mode 100644
index 0000000..df8e3d1
--- /dev/null
+++ b/script/sql/drop/8.tags.sql
@@ -0,0 +1,5 @@
+-- [TAGS]
+
+DROP TABLE IF EXISTS TAGS_LINK;
+
+DROP TABLE IF EXISTS TAGS_NODE;
diff --git a/script/sql/drop/9.demands.sql b/script/sql/drop/9.demands.sql
new file mode 100644
index 0000000..ebe0209
--- /dev/null
+++ b/script/sql/drop/9.demands.sql
@@ -0,0 +1,3 @@
+-- [DEMANDS]
+
+DROP TABLE IF EXISTS DEMANDS;
diff --git a/script/sql/drop/operation.sql b/script/sql/drop/operation.sql
new file mode 100644
index 0000000..998ee2f
--- /dev/null
+++ b/script/sql/drop/operation.sql
@@ -0,0 +1,7 @@
+DROP TABLE IF EXISTS TRANSACTION_OPERATION;
+
+DROP TABLE IF EXISTS SNAPSHOT_OPERATION;
+
+DROP TABLE IF EXISTS CURRENT_OPERATION;
+
+DROP TABLE IF EXISTS OPERATION;
diff --git a/script/sql/section_drop/1.title.sql b/script/sql/section_drop/1.title.sql
deleted file mode 100644
index 215ecc6..0000000
--- a/script/sql/section_drop/1.title.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- [TITLE]
-
-DROP TABLE TITLE;
diff --git a/script/sql/section_drop/10.status.sql b/script/sql/section_drop/10.status.sql
deleted file mode 100644
index 970330e..0000000
--- a/script/sql/section_drop/10.status.sql
+++ /dev/null
@@ -1,13 +0,0 @@
--- [STATUS]
-
-DROP TABLE STATUS_LINK;
-
-DROP TABLE STATUS_VALVE;
-
-DROP TYPE STATUS_VALVE_STATUS;
-
-DROP TABLE STATUS_PUMP;
-
-DROP TABLE STATUS_PIPE;
-
-DROP TYPE STATUS_PIPE_PUMP_STATUS;
diff --git a/script/sql/section_drop/11.patterns.sql b/script/sql/section_drop/11.patterns.sql
deleted file mode 100644
index 565c67e..0000000
--- a/script/sql/section_drop/11.patterns.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- [PATTERNS]
-
-DROP TABLE PATTERNS;
diff --git a/script/sql/section_drop/12.curves.sql b/script/sql/section_drop/12.curves.sql
deleted file mode 100644
index 9535588..0000000
--- a/script/sql/section_drop/12.curves.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- [CURVES]
-
-DROP TABLE CURVES;
diff --git a/script/sql/section_drop/13.controls.sql b/script/sql/section_drop/13.controls.sql
deleted file mode 100644
index 5333175..0000000
--- a/script/sql/section_drop/13.controls.sql
+++ /dev/null
@@ -1,9 +0,0 @@
--- [CONTROLS]
-
-DROP TABLE CONTROLS_3;
-
-DROP TABLE CONTROLS_2;
-
-DROP TABLE CONTROLS_1;
-
-DROP TYPE CONTROLS_1_PREP;
diff --git a/script/sql/section_drop/14.rules.sql b/script/sql/section_drop/14.rules.sql
deleted file mode 100644
index 7cc4bac..0000000
--- a/script/sql/section_drop/14.rules.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- [RULES]
-
-DROP TABLE RULES;
diff --git a/script/sql/section_drop/15.energy.sql b/script/sql/section_drop/15.energy.sql
deleted file mode 100644
index 1da9af8..0000000
--- a/script/sql/section_drop/15.energy.sql
+++ /dev/null
@@ -1,9 +0,0 @@
--- [ENERGY]
-
-DROP TABLE ENERGY_DEMAND_CHARGE;
-
-DROP TABLE ENERGY_PUMP;
-
-DROP TABLE ENERGY_GLOBAL;
-
-DROP TYPE ENERGY_PARAM;
diff --git a/script/sql/section_drop/16.emitters.sql b/script/sql/section_drop/16.emitters.sql
deleted file mode 100644
index 7aa46f8..0000000
--- a/script/sql/section_drop/16.emitters.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- [EMITTERS]
-
-DROP TABLE EMITTERS;
diff --git a/script/sql/section_drop/17.quality.sql b/script/sql/section_drop/17.quality.sql
deleted file mode 100644
index c15ac7d..0000000
--- a/script/sql/section_drop/17.quality.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- [QUALITY]
-
-DROP TABLE QUALITY;
diff --git a/script/sql/section_drop/18.sources.sql b/script/sql/section_drop/18.sources.sql
deleted file mode 100644
index e11b7ea..0000000
--- a/script/sql/section_drop/18.sources.sql
+++ /dev/null
@@ -1,5 +0,0 @@
--- [SOURCES]
-
-DROP TABLE SOURCES;
-
-DROP TYPE SOURCES_TYPE;
diff --git a/script/sql/section_drop/19.reactions.sql b/script/sql/section_drop/19.reactions.sql
deleted file mode 100644
index bcc9dc5..0000000
--- a/script/sql/section_drop/19.reactions.sql
+++ /dev/null
@@ -1,19 +0,0 @@
--- [REACTIONS]
-
-DROP TABLE REACTIONS_ROUGHNESS_CORRELATION;
-
-DROP TABLE REACTIONS_LIMITING_POTENTIAL;
-
-DROP TABLE REACTIONS_TANK;
-
-DROP TABLE REACTIONS_PIPE;
-
-DROP TYPE REACTIONS_PIPE_PARAM;
-
-DROP TABLE REACTIONS_GLOBAL;
-
-DROP TYPE REACTIONS_GLOBAL_PARAM;
-
-DROP TABLE REACTIONS_ORDER;
-
-DROP TYPE REACTIONS_ORDER_PARAM;
diff --git a/script/sql/section_drop/2.junctions.sql b/script/sql/section_drop/2.junctions.sql
deleted file mode 100644
index 8fc23c4..0000000
--- a/script/sql/section_drop/2.junctions.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- [JUNCTIONS]
-
-DROP TABLE JUNCTIONS;
diff --git a/script/sql/section_drop/20.mixing.sql b/script/sql/section_drop/20.mixing.sql
deleted file mode 100644
index 1434859..0000000
--- a/script/sql/section_drop/20.mixing.sql
+++ /dev/null
@@ -1,5 +0,0 @@
--- [MIXING]
-
-DROP TABLE MIXING;
-
-DROP TYPE MIXING_Model;
diff --git a/script/sql/section_drop/21.times.sql b/script/sql/section_drop/21.times.sql
deleted file mode 100644
index 0d45aed..0000000
--- a/script/sql/section_drop/21.times.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- [TIMES]
-
-DROP TABLE TIMES;
diff --git a/script/sql/section_drop/22.report.sql b/script/sql/section_drop/22.report.sql
deleted file mode 100644
index 58dcd51..0000000
--- a/script/sql/section_drop/22.report.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- [REPORT]
-
-DROP TABLE REPORT;
diff --git a/script/sql/section_drop/23.options.sql b/script/sql/section_drop/23.options.sql
deleted file mode 100644
index 69e9714..0000000
--- a/script/sql/section_drop/23.options.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- [OPTIONS]
-
-DROP TABLE OPTIONS;
diff --git a/script/sql/section_drop/24.coordinates.sql b/script/sql/section_drop/24.coordinates.sql
deleted file mode 100644
index 59f9f45..0000000
--- a/script/sql/section_drop/24.coordinates.sql
+++ /dev/null
@@ -1,7 +0,0 @@
--- [COORDINATES]
-
-DROP INDEX COORDINATES_GIST;
-
-DROP INDEX COORDINATES_SPGIST;
-
-DROP TABLE COORDINATES;
diff --git a/script/sql/section_drop/25.vertices.sql b/script/sql/section_drop/25.vertices.sql
deleted file mode 100644
index 1352d0d..0000000
--- a/script/sql/section_drop/25.vertices.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- [VERTICES]
-
-DROP TABLE VERTICES;
diff --git a/script/sql/section_drop/26.labels.sql b/script/sql/section_drop/26.labels.sql
deleted file mode 100644
index 70da104..0000000
--- a/script/sql/section_drop/26.labels.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- [LABELS]
-
-DROP TABLE LABELS;
diff --git a/script/sql/section_drop/27.backdrop.sql b/script/sql/section_drop/27.backdrop.sql
deleted file mode 100644
index 85f3bf2..0000000
--- a/script/sql/section_drop/27.backdrop.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- [BACKDROP]
-
-DROP TABLE BACKDROP;
diff --git a/script/sql/section_drop/3.reservoirs.sql b/script/sql/section_drop/3.reservoirs.sql
deleted file mode 100644
index 4fd1e46..0000000
--- a/script/sql/section_drop/3.reservoirs.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- [RESERVOIRS]
-
-DROP TABLE RESERVOIRS;
diff --git a/script/sql/section_drop/4.tanks.sql b/script/sql/section_drop/4.tanks.sql
deleted file mode 100644
index f9a4c27..0000000
--- a/script/sql/section_drop/4.tanks.sql
+++ /dev/null
@@ -1,5 +0,0 @@
--- [TANKS]
-
-DROP TABLE TANKS;
-
-DROP TYPE TANKS_OVERFLOW;
diff --git a/script/sql/section_drop/5.pipes.sql b/script/sql/section_drop/5.pipes.sql
deleted file mode 100644
index e01acd3..0000000
--- a/script/sql/section_drop/5.pipes.sql
+++ /dev/null
@@ -1,5 +0,0 @@
--- [PIPES]
-
-DROP TABLE PIPES;
-
-DROP TYPE PIPES_STATUS;
diff --git a/script/sql/section_drop/6.pumps.sql b/script/sql/section_drop/6.pumps.sql
deleted file mode 100644
index 2526df6..0000000
--- a/script/sql/section_drop/6.pumps.sql
+++ /dev/null
@@ -1,11 +0,0 @@
--- [PUMPS]
-
-DROP TABLE PUMPS_PROPERTY_PATTERN;
-
-DROP TABLE PUMPS_PROPERTY_HEAD;
-
-DROP TABLE PUMPS_PROPERTY_SPEED;
-
-DROP TABLE PUMPS_PROPERTY_POWER;
-
-DROP TABLE PUMPS;
diff --git a/script/sql/section_drop/7.valves.sql b/script/sql/section_drop/7.valves.sql
deleted file mode 100644
index ca001fe..0000000
--- a/script/sql/section_drop/7.valves.sql
+++ /dev/null
@@ -1,5 +0,0 @@
--- [VALVES]
-
-DROP TABLE VALVES;
-
-DROP TYPE VALVES_TYPE;
diff --git a/script/sql/section_drop/8.tags.sql b/script/sql/section_drop/8.tags.sql
deleted file mode 100644
index 78ec688..0000000
--- a/script/sql/section_drop/8.tags.sql
+++ /dev/null
@@ -1,5 +0,0 @@
--- [TAGS]
-
-DROP TABLE TAGS_LINK;
-
-DROP TABLE TAGS_NODE;
diff --git a/script/sql/section_drop/9.demands.sql b/script/sql/section_drop/9.demands.sql
deleted file mode 100644
index 7276cca..0000000
--- a/script/sql/section_drop/9.demands.sql
+++ /dev/null
@@ -1,3 +0,0 @@
--- [DEMANDS]
-
-DROP TABLE DEMANDS;
diff --git a/script/template.py b/script/template.py
new file mode 100644
index 0000000..c219802
--- /dev/null
+++ b/script/template.py
@@ -0,0 +1,102 @@
+import psycopg as pg
+
+sql_create = [
+    "sql/create/0.base.sql",
+    "sql/create/1.title.sql",
+    "sql/create/2.junctions.sql",
+    "sql/create/3.reservoirs.sql",
+    "sql/create/4.tanks.sql",
+    "sql/create/5.pipes.sql",
+    "sql/create/6.pumps.sql",
+    "sql/create/7.valves.sql",
+    "sql/create/8.tags.sql",
+    "sql/create/9.demands.sql",
+    "sql/create/10.status.sql",
+    "sql/create/11.patterns.sql",
+    "sql/create/12.curves.sql",
+    "sql/create/13.controls.sql",
+    "sql/create/14.rules.sql",
+    "sql/create/15.energy.sql",
+    "sql/create/16.emitters.sql",
+    "sql/create/17.quality.sql",
+    "sql/create/18.sources.sql",
+    "sql/create/19.reactions.sql",
+    "sql/create/20.mixing.sql",
+    "sql/create/21.times.sql",
+    "sql/create/22.report.sql",
+    "sql/create/23.options.sql",
+    "sql/create/24.coordinates.sql",
+    "sql/create/25.vertices.sql",
+    "sql/create/26.labels.sql",
+    "sql/create/27.backdrop.sql",
+    "sql/create/28.end.sql",
+    "sql/create/operation.sql"
+]
+
+sql_drop = [
+    "sql/drop/operation.sql",
+    "sql/drop/28.end.sql",
+    "sql/drop/27.backdrop.sql",
+    "sql/drop/26.labels.sql",
+    "sql/drop/25.vertices.sql",
+    "sql/drop/24.coordinates.sql",
+    "sql/drop/23.options.sql",
+    "sql/drop/22.report.sql",
+    "sql/drop/21.times.sql",
+    "sql/drop/20.mixing.sql",
+    "sql/drop/19.reactions.sql",
+    "sql/drop/18.sources.sql",
+    "sql/drop/17.quality.sql",
+    "sql/drop/16.emitters.sql",
+    "sql/drop/15.energy.sql",
+    "sql/drop/14.rules.sql",
+    "sql/drop/13.controls.sql",
+    "sql/drop/12.curves.sql",
+    "sql/drop/11.patterns.sql",
+    "sql/drop/10.status.sql",
+    "sql/drop/9.demands.sql",
+    "sql/drop/8.tags.sql",
+    "sql/drop/7.valves.sql",
+    "sql/drop/6.pumps.sql",
+    "sql/drop/5.pipes.sql",
+    "sql/drop/4.tanks.sql",
+    "sql/drop/3.reservoirs.sql",
+    "sql/drop/2.junctions.sql",
+    "sql/drop/1.title.sql",
+    "sql/drop/0.base.sql"
+]
+
+def create_template():
+    with pg.connect(conninfo="dbname=postgres", autocommit=True) as conn:
+        with conn.cursor() as cur:
+            cur.execute("create database project")
+    with pg.connect(conninfo="dbname=project") as conn:
+        with conn.cursor() as cur:
+            for sql in sql_create:
+                with open(sql, "r") as f:
+                    cur.execute(f.read())
+                print(f'executed {sql}')
+        conn.commit()
+
+def have_template():
+    with pg.connect(conninfo="dbname=postgres", autocommit=True) as conn:
+        with conn.cursor() as cur:
+            cur.execute("select * from pg_database where datname = 'project'")
+            return cur.rowcount > 0
+
+def delete_template():
+    with pg.connect(conninfo="dbname=project") as conn:
+        with conn.cursor() as cur:
+            for sql in sql_drop:
+                with open(sql, "r") as f:
+                    cur.execute(f.read())
+                print(f'executed {sql}')
+        conn.commit()
+    with pg.connect(conninfo="dbname=postgres", autocommit=True) as conn:
+        with conn.cursor() as cur:
+            cur.execute("drop database project")
+
+if __name__ == "__main__":
+    if (have_template()):
+        delete_template()
+    create_template()
diff --git a/script/tjnetwork_admin.py b/script/tjnetwork_admin.py
deleted file mode 100644
index c32f6e2..0000000
--- a/script/tjnetwork_admin.py
+++ /dev/null
@@ -1,89 +0,0 @@
-import psycopg as pg
-
-sql_create = [
-    "sql/base_create.sql",
-    "sql/section_create/1.title.sql",
-    "sql/section_create/2.junctions.sql",
-    "sql/section_create/3.reservoirs.sql",
-    "sql/section_create/4.tanks.sql",
-    "sql/section_create/5.pipes.sql",
-    "sql/section_create/6.pumps.sql",
-    "sql/section_create/7.valves.sql",
-    "sql/section_create/8.tags.sql",
-    "sql/section_create/9.demands.sql",
-    "sql/section_create/10.status.sql",
-    "sql/section_create/11.patterns.sql",
-    "sql/section_create/12.curves.sql",
-    "sql/section_create/13.controls.sql",
-    "sql/section_create/14.rules.sql",
-    "sql/section_create/15.energy.sql",
-    "sql/section_create/16.emitters.sql",
-    "sql/section_create/17.quality.sql",
-    "sql/section_create/18.sources.sql",
-    "sql/section_create/19.reactions.sql",
-    "sql/section_create/20.mixing.sql",
-    "sql/section_create/21.times.sql",
-    "sql/section_create/22.report.sql",
-    "sql/section_create/23.options.sql",
-    "sql/section_create/24.coordinates.sql",
-    "sql/section_create/25.vertices.sql",
-    "sql/section_create/26.labels.sql",
-    "sql/section_create/27.backdrop.sql",
-    "sql/section_create/28.end.sql"
-]
-
-sql_drop = [
-    "sql/section_drop/28.end.sql",
-    "sql/section_drop/27.backdrop.sql",
-    "sql/section_drop/26.labels.sql",
-    "sql/section_drop/25.vertices.sql",
-    "sql/section_drop/24.coordinates.sql",
-    "sql/section_drop/23.options.sql",
-    "sql/section_drop/22.report.sql",
-    "sql/section_drop/21.times.sql",
-    "sql/section_drop/20.mixing.sql",
-    "sql/section_drop/19.reactions.sql",
-    "sql/section_drop/18.sources.sql",
-    "sql/section_drop/17.quality.sql",
-    "sql/section_drop/16.emitters.sql",
-    "sql/section_drop/15.energy.sql",
-    "sql/section_drop/14.rules.sql",
-    "sql/section_drop/13.controls.sql",
-    "sql/section_drop/12.curves.sql",
-    "sql/section_drop/11.patterns.sql",
-    "sql/section_drop/10.status.sql",
-    "sql/section_drop/9.demands.sql",
-    "sql/section_drop/8.tags.sql",
-    "sql/section_drop/7.valves.sql",
-    "sql/section_drop/6.pumps.sql",
-    "sql/section_drop/5.pipes.sql",
-    "sql/section_drop/4.tanks.sql",
-    "sql/section_drop/3.reservoirs.sql",
-    "sql/section_drop/2.junctions.sql",
-    "sql/section_drop/1.title.sql",
-    "sql/base_drop.sql"
-]
-
-def create_template():
-    with pg.connect(conninfo="dbname=postgres", autocommit=True) as conn:
-        with conn.cursor() as cur:
-            cur.execute(f"create database project")
-    with pg.connect(conninfo=f"dbname=project") as conn:
-        with conn.cursor() as cur:
-            for sql in sql_create:
-                with open(sql, "r") as f:
-                    cur.execute(f.read())
-                print(f'executed {sql}')
-        conn.commit()
-
-def delete_template():
-    with pg.connect(conninfo=f"dbname=project") as conn:
-        with conn.cursor() as cur:
-            for sql in sql_drop:
-                with open(sql, "r") as f:
-                    cur.execute(f.read())
-                print(f'executed {sql}')
-        conn.commit()
-    with pg.connect(conninfo="dbname=postgres", autocommit=True) as conn:
-        with conn.cursor() as cur:
-            cur.execute(f"drop database project")
diff --git a/tjnetwork_new.py b/tjnetwork_new.py
new file mode 100644
index 0000000..c47d573
--- /dev/null
+++ b/tjnetwork_new.py
@@ -0,0 +1,171 @@
+from msilib.schema import CheckBox
+import api
+
+
+############################################################
+# ChangeSet
+############################################################
+
+ChangeSet = api.ChangeSet
+
+
+############################################################
+# enum
+############################################################
+
+JUNCTION = api.JUNCTION
+RESERVOIR = api.RESERVOIR
+TANK = api.TANK
+PIPE = api.PIPE
+PUMP = api.PUMP
+VALVE = api.VALVE
+
+
+############################################################
+# project
+############################################################
+
+def have_project(name: str) -> bool:
+    return api.have_project(name)
+
+def create_project(name: str) -> None:
+    return api.create_project(name)
+
+def delete_project(name: str) -> None:
+    return api.delete_project(name)
+
+def is_project_open(name: str) -> bool:
+    return api.is_project_open(name)
+
+def open_project(name: str) -> None:
+    return api.open_project(name)
+
+def close_project(name: str) -> None:
+    return api.close_project(name)
+
+def copy_project(source: str, new: str) -> None:
+    return api.copy_project(source, new)
+
+
+############################################################
+# operation
+############################################################
+
+def undo(name: str) -> None:
+    return api.undo(name)
+
+def redo(name: str) -> None:
+    return api.redo(name)
+
+def have_snapshot(name: str, tag: str) -> bool:
+    return api.have_snapshot(name, tag)
+
+def take_snapshot(name: str, tag: str) -> None:
+    return api.take_snapshot(name, tag)
+
+def pick_snapshot(name: str, tag: str) -> None:
+    return api.pick_snapshot(name, tag)
+
+def have_transaction(name: str) -> bool:
+    return api.have_transaction(name)
+
+def start_transaction(name: str, strict: bool = False) -> None:
+    return api.start_transaction(name, strict)
+
+def commit_transaction(name: str) -> None:
+    return api.commit_transaction(name)
+
+def abort_transaction(name: str) -> None:
+    return api.abort_transaction(name)
+
+############################################################
+# type
+############################################################
+
+def is_node(name: str, node_id: str) -> bool:
+    return api.is_node(name, node_id)
+
+def is_junction(name: str, node_id: str) -> bool:
+    return api.is_junction(name, node_id)
+
+def is_reservoir(name: str, node_id: str) -> bool:
+    return api.is_reservoir(name, node_id)
+
+def is_tank(name: str, node_id: str) -> bool:
+    return api.is_tank(name, node_id)
+
+def is_link(name: str, link_id: str) -> bool:
+    return api.is_link(name, link_id)
+
+def is_pipe(name: str, link_id: str) -> bool:
+    return api.is_pipe(name, link_id)
+
+def is_pump(name: str, link_id: str) -> bool:
+    return api.is_pump(name, link_id)
+
+def is_valve(name: str, link_id: str) -> bool:
+    return api.is_valve(name, link_id)
+
+def is_curve(name: str, curve_id: str) -> bool:
+    return api.is_curve(name, curve_id)
+
+def is_pattern(name: str, pattern_id: str) -> bool:
+    return api.is_pattern(name, pattern_id)
+
+def get_nodes(name: str) -> list[str]:
+    return api.get_nodes(name)
+
+def get_links(name: str) -> list[str]:
+    return api.get_links(name)
+
+def get_curves(name: str) -> list[str]:
+    return api.get_curves(name)
+
+def get_patterns(name: str) -> list[str]:
+    return api.get_patterns(name)
+
+
+############################################################
+# title 1.[TITLE]
+############################################################
+
+def set_title(name: str, title: str) -> ChangeSet:
+    return api.set_title(name, title)
+
+def get_title(name: str) -> str:
+    return api.get_title(name)
+
+
+############################################################
+# junction 2.[JUNCTIONS]
+############################################################
+
+def add_junction(name: str, junction_id: str, x: float, y: float, elevation: float) -> ChangeSet:
+    return api.add_junction(name, junction_id, x, y, elevation)
+
+def delete_junction(name: str, junction_id: str) -> ChangeSet:
+    return api.delete_junction(name, junction_id)
+
+def get_junction_elevation(name: str, junction_id: str) -> float | None:
+    return api.get_junction_elevation(name, junction_id)
+
+def get_junction_demand(name: str, junction_id: str) -> float | str | None:
+    return api.get_junction_demand(name, junction_id)
+
+def get_junction_pattern(name: str, junction_id: str) -> str | None:
+    return api.get_junction_pattern(name, junction_id)
+
+def get_junction_coord(name: str, junction_id: str) -> dict[str, float] | None:
+    return api.get_junction_coord(name, junction_id)
+
+def set_junction_elevation(name: str, junction_id: str, elevation: float) -> ChangeSet:
+    return api.set_junction_elevation(name, junction_id, elevation)
+
+def set_junction_demand(name: str, junction_id: str, demand: float) -> ChangeSet:
+    return api.set_junction_demand(name, junction_id, demand)
+
+def set_junction_pattern(name: str, junction_id: str, pattern: str) -> ChangeSet:
+    return api.set_junction_pattern(name, junction_id, pattern)
+
+def set_junction_coord(name: str, junction_id: str, x: float, y: float) -> ChangeSet:
+    return api.set_junction_coord(name, junction_id, x, y)