diff --git a/api/__init__.py b/api/__init__.py
index e31759f..4f2c38b 100644
--- a/api/__init__.py
+++ b/api/__init__.py
@@ -38,6 +38,9 @@ from .s6_pumps import get_pump_schema, add_pump, get_pump, set_pump, delete_pump
 from .s7_valves import VALVES_TYPE_PRV, VALVES_TYPE_PSV, VALVES_TYPE_PBV, VALVES_TYPE_FCV, VALVES_TYPE_TCV, VALVES_TYPE_GPV
 from .s7_valves import get_valve_schema, add_valve, get_valve, set_valve, delete_valve
 
+from .s8_tags import TAG_TYPE_NODE, TAG_TYPE_LINK
+from .s8_tags import get_tag_schema, get_tag, set_tag
+
 from .s9_demands import get_demand_schema, get_demand, set_demand
 
 from .s10_status import LINK_STATUS_OPEN, LINK_STATUS_CLOSED, LINK_STATUS_ACTIVE
diff --git a/api/s8_tags.py b/api/s8_tags.py
new file mode 100644
index 0000000..67b53b0
--- /dev/null
+++ b/api/s8_tags.py
@@ -0,0 +1,79 @@
+from .operation import *
+
+TAG_TYPE_NODE = 'NODE'
+TAG_TYPE_LINK = 'LINK'
+
+def get_tag_schema(name: str) -> dict[str, dict[str, Any]]:
+    return { 't_type' : {'type': 'str' , 'optional': False , 'readonly': False},
+             'id'     : {'type': 'str' , 'optional': False , 'readonly': False},
+             'tag'    : {'type': 'str' , 'optional': True , 'readonly': False},}
+
+
+def get_tag(name: str, t_type: str, id: str) -> dict[str, Any]:
+    t = None
+    if t_type == TAG_TYPE_NODE:
+        t = try_read(name, f"select * from tags_node where id = '{id}'")
+    elif t_type == TAG_TYPE_LINK:
+        t = try_read(name, f"select * from tags_link where id = '{id}'")
+    else:
+        raise Exception('Only support NODE and Link')
+    if t == None:
+        return { 't_type': t_type, 'id': id, 'tag': None }
+    d = {}
+    d['t_type'] = t_type
+    d['id'] = str(t['id'])
+    d['tag'] = str(t['tag']) if t['tag'] != None else None
+    return d
+
+
+class Tag(object):
+    def __init__(self, input: dict[str, Any]) -> None:
+        self.type = 'tag'
+        self.t_type = str(input['t_type'])
+        self.id = str(input['id'])
+        self.tag = str(input['tag']) if 'tag' in input and input['tag'] != None else None
+
+        self.f_type = f"'{self.type}'"
+        self.f_t_type = f"'{self.t_type}'"
+        self.f_id = f"'{self.id}'"
+        self.f_tag = f"'{self.tag}'" if self.tag != None else 'null'
+
+    def as_dict(self) -> dict[str, Any]:
+        return { 'type': self.type, 't_type': self.t_type, 'id': self.id, 'tag': self.tag }
+
+
+def set_tag_cache(name: str, cs: ChangeSet) -> SqlChangeSet:
+    old = Tag(get_tag(name, cs.operations[0]['t_type'], cs.operations[0]['id']))
+    raw_new = get_tag(name, cs.operations[0]['t_type'], cs.operations[0]['id'])
+
+    new_dict = cs.operations[0]
+    schema = get_tag_schema(name)
+    for key, value in schema.items():
+        if key in new_dict and not value['readonly']:
+            raw_new[key] = new_dict[key]
+    new = Tag(raw_new)
+
+    table = ''
+    if cs.operations[0]['t_type'] == TAG_TYPE_NODE:
+        table = 'tags_node'
+    elif cs.operations[0]['t_type'] == TAG_TYPE_LINK:
+        table = 'tags_link'
+    else:
+        raise Exception('Only support NODE and Link')
+
+    redo_sql = f"delete from {table} where id = {new.f_id};"
+    if new.tag != None:
+        redo_sql += f"\ninsert into {table} (id, tag) values ({new.f_id}, {new.f_tag});"
+
+    undo_sql = f"delete from {table} where id = {old.f_id};"
+    if old.tag != None:
+        undo_sql += f"\ninsert into {table} (id, tag) values ({old.f_id}, {old.f_tag});"
+
+    redo_cs = g_update_prefix | new.as_dict()
+    undo_cs = g_update_prefix | old.as_dict()
+
+    return SqlChangeSet(redo_sql, undo_sql, redo_cs, undo_cs)
+
+
+def set_tag(name: str, cs: ChangeSet) -> ChangeSet:
+    return execute_command(name, set_tag_cache(name, cs))
diff --git a/test_tjnetwork.py b/test_tjnetwork.py
index 918f547..e33b971 100644
--- a/test_tjnetwork.py
+++ b/test_tjnetwork.py
@@ -1174,6 +1174,89 @@ class TestApi:
         self.leave(p)
 
 
+    def test_tag(self):
+        p = 'test_tag'
+        self.enter(p)
+
+        add_junction(p, ChangeSet({'id': 'j1', 'x': 0.0, 'y': 10.0, 'elevation': 20.0}))
+        add_junction(p, ChangeSet({'id': 'j2', 'x': 0.0, 'y': 10.0, 'elevation': 20.0}))
+        assert is_junction(p, 'j1')
+        assert is_junction(p, 'j2')
+
+        add_pipe(p, ChangeSet({'id': 'p0', 'node1': 'j1', 'node2': 'j2', 'length': 100.0, 'diameter': 10.0, 'roughness': 0.1, 'minor_loss': 0.5, 'status': PIPE_STATUS_OPEN }))
+        assert is_pipe(p, 'p0')
+
+        t = get_tag(p, TAG_TYPE_NODE, 'j1')
+        assert t['tag'] == None
+        set_tag(p, ChangeSet({'t_type': TAG_TYPE_NODE, 'id': 'j1', 'tag': 'j1t' }))
+        t = get_tag(p, TAG_TYPE_NODE, 'j1')
+        assert t['tag'] == 'j1t'
+
+        t = get_tag(p, TAG_TYPE_NODE, 'j2')
+        assert t['tag'] == None
+        set_tag(p, ChangeSet({'t_type': TAG_TYPE_NODE, 'id': 'j2', 'tag': 'j2t' }))
+        t = get_tag(p, TAG_TYPE_NODE, 'j2')
+        assert t['tag'] == 'j2t'
+
+        t = get_tag(p, TAG_TYPE_LINK, 'p0')
+        assert t['tag'] == None
+        set_tag(p, ChangeSet({'t_type': TAG_TYPE_LINK, 'id': 'p0', 'tag': 'p0t' }))
+        t = get_tag(p, TAG_TYPE_LINK, 'p0')
+        assert t['tag'] == 'p0t'
+
+        self.leave(p)
+
+    def test_tag_op(self):
+        p = 'test_tag_op'
+        self.enter(p)
+
+        add_junction(p, ChangeSet({'id': 'j1', 'x': 0.0, 'y': 10.0, 'elevation': 20.0}))
+        add_junction(p, ChangeSet({'id': 'j2', 'x': 0.0, 'y': 10.0, 'elevation': 20.0}))
+        assert is_junction(p, 'j1')
+        assert is_junction(p, 'j2')
+
+        add_pipe(p, ChangeSet({'id': 'p0', 'node1': 'j1', 'node2': 'j2', 'length': 100.0, 'diameter': 10.0, 'roughness': 0.1, 'minor_loss': 0.5, 'status': PIPE_STATUS_OPEN }))
+        assert is_pipe(p, 'p0')
+
+        cs = set_tag(p, ChangeSet({'t_type': TAG_TYPE_NODE, 'id': 'j1', 'tag': 'j1t' })).operations[0]
+        assert cs['type'] == 'tag'
+        assert cs['t_type'] == TAG_TYPE_NODE
+        assert cs['id'] == 'j1'
+        assert cs['tag'] == 'j1t'
+
+        cs = execute_undo(p).operations[0]
+        assert cs['type'] == 'tag'
+        assert cs['t_type'] == TAG_TYPE_NODE
+        assert cs['id'] == 'j1'
+        assert cs['tag'] == None
+
+        cs = execute_redo(p).operations[0]
+        assert cs['type'] == 'tag'
+        assert cs['t_type'] == TAG_TYPE_NODE
+        assert cs['id'] == 'j1'
+        assert cs['tag'] == 'j1t'
+
+        cs = set_tag(p, ChangeSet({'t_type': TAG_TYPE_LINK, 'id': 'p0', 'tag': 'p0t' })).operations[0]
+        assert cs['type'] == 'tag'
+        assert cs['t_type'] == TAG_TYPE_LINK
+        assert cs['id'] == 'p0'
+        assert cs['tag'] == 'p0t'
+
+        cs = execute_undo(p).operations[0]
+        assert cs['type'] == 'tag'
+        assert cs['t_type'] == TAG_TYPE_LINK
+        assert cs['id'] == 'p0'
+        assert cs['tag'] == None
+
+        cs = execute_redo(p).operations[0]
+        assert cs['type'] == 'tag'
+        assert cs['t_type'] == TAG_TYPE_LINK
+        assert cs['id'] == 'p0'
+        assert cs['tag'] == 'p0t'
+
+        self.leave(p)
+
+
     def test_demand(self):
         p = 'test_demand'
         self.enter(p)
diff --git a/tjnetwork.py b/tjnetwork.py
index 9f88c8e..7579f49 100644
--- a/tjnetwork.py
+++ b/tjnetwork.py
@@ -40,6 +40,9 @@ VALVES_TYPE_FCV = api.VALVES_TYPE_FCV
 VALVES_TYPE_TCV = api.VALVES_TYPE_TCV
 VALVES_TYPE_GPV = api.VALVES_TYPE_GPV
 
+TAG_TYPE_NODE = api.TAG_TYPE_NODE
+TAG_TYPE_LINK = api.TAG_TYPE_LINK
+
 LINK_STATUS_OPEN = api.LINK_STATUS_OPEN
 LINK_STATUS_CLOSED = api.LINK_STATUS_CLOSED
 LINK_STATUS_ACTIVE = api.LINK_STATUS_ACTIVE
@@ -334,6 +337,23 @@ def delete_valve(name: str, cs: ChangeSet) -> ChangeSet:
     return api.delete_valve(name, cs)
 
 
+############################################################
+# tag 8.[TAGS]
+############################################################
+
+def get_tag_schema(name: str) -> dict[str, dict[str, Any]]:
+    return api.get_tag_schema(name)
+
+def get_tag(name: str, t_type: str, id: str) -> dict[str, Any]:
+    return api.get_tag(name, t_type, id)
+
+# example:
+# set_tag(p, ChangeSet({'t_type': TAG_TYPE_NODE, 'id': 'j1', 'tag': 'j1t' }))
+# set_tag(p, ChangeSet({'t_type': TAG_TYPE_LINK, 'id': 'p0', 'tag': 'p0t' }))
+def set_tag(name: str, cs: ChangeSet) -> ChangeSet:
+    return api.set_tag(name, cs)
+
+
 ############################################################
 # demand 9.[DEMANDS]
 ############################################################