diff --git a/server/entertainment_decider/models/extras/__init__.py b/server/entertainment_decider/models/extras/__init__.py
index 5c0f8cb..016168c 100644
--- a/server/entertainment_decider/models/extras/__init__.py
+++ b/server/entertainment_decider/models/extras/__init__.py
@@ -1,8 +1,24 @@
+from .exids_base import (
+    ExIdKey_Columns,
+    ExIdKeyCompatible,
+    ExIdKeyData,
+    ExIdKeyDict,
+    ExIdKeyTuple,
+    new_ExIdKey,
+    pack_ExIdKey,
+)
 from .uris import (
     UriHolder,
 )
 
 
 __all__ = [
+    "ExIdKey_Columns",
+    "ExIdKeyCompatible",
+    "ExIdKeyData",
+    "ExIdKeyDict",
+    "ExIdKeyTuple",
     "UriHolder",
+    "new_ExIdKey",
+    "pack_ExIdKey",
 ]
diff --git a/server/entertainment_decider/models/extras/exids_base.py b/server/entertainment_decider/models/extras/exids_base.py
new file mode 100644
index 0000000..e46fc57
--- /dev/null
+++ b/server/entertainment_decider/models/extras/exids_base.py
@@ -0,0 +1,172 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import (
+    Optional,
+    Protocol,
+    Tuple,
+    Type,
+    TypeAlias,
+    TypeVar,
+    TypedDict,
+    Unpack,
+)
+
+from pony import orm
+
+
+WIKIDATA_PROPERTY_PREFIX = "org.wikidata/property"
+
+T = TypeVar("T")
+
+
+# attributes & docstrings need to be synced (manually)
+# all occassions are tagged with SYNC:ExIdKey:Properties
+
+
+ExIdKeyTuple: TypeAlias = Tuple[bool, str]
+
+
+class ExIdKeyDict(TypedDict):
+    # SYNC:ExIdKey:Properties
+    wikidata_prop: bool
+    """
+    `True` if key_name is a wikidata property,
+    `False` if key_name is a canonical key name.
+    """
+    key_name: str
+    """
+    key name for external identifier
+
+    Should be used externally.
+    Should be unique worldwide, but one per external identifier.
+
+    Can either be a Wikidata property id (starting with `P`),
+    otherwise a canonical key names (see `docs/canonical_exids.md`).
+    """
+
+
+class ExIdKeyData(Protocol):
+    # SYNC:ExIdKey:Properties
+    wikidata_prop: bool
+    """
+    `True` if key_name is a wikidata property,
+    `False` if key_name is a canonical key name.
+    """
+    key_name: str
+    """
+    key name for external identifier
+
+    Should be used externally.
+    Should be unique worldwide, but one per external identifier.
+
+    Can either be a Wikidata property id (starting with `P`),
+    otherwise a canonical key names (see `docs/canonical_exids.md`).
+    """
+
+    @property
+    def key_map(self) -> ExIdKeyDict:
+        # SYNC:ExIdKey:Properties
+        return {
+            "wikidata_prop": self.wikidata_prop,
+            "key_name": self.key_name,
+        }
+
+    @property
+    def key_data_copy(self) -> ExIdKeyData:
+        return pack_ExIdKey(key_data=self.key_map)
+
+    @property
+    def key_str(self) -> str:
+        # SYNC:ExIdKey:Properties
+        return (
+            WIKIDATA_PROPERTY_PREFIX + ":" if self.wikidata_prop else ""
+        ) + self.key_name
+
+
+ExIdKeyCompatible: TypeAlias = ExIdKeyTuple | ExIdKeyDict | ExIdKeyData
+
+
+@dataclass
+class ExIdKey_Native(ExIdKeyData):
+    """implementer of ExIdKeyProto as dataclass"""
+
+    # SYNC:ExIdKey:Properties
+    wikidata_prop: bool
+    """
+    `True` if key_name is a wikidata property,
+    `False` if key_name is a canonical key name.
+    """
+    key_name: str
+    """
+    key name for external identifier
+
+    Should be used externally.
+    Should be unique worldwide, but one per external identifier.
+
+    Can either be a Wikidata property id (starting with `P`),
+    otherwise a canonical key names (see `docs/canonical_exids.md`).
+    """
+
+
+def new_ExIdKey(**kwargs: Unpack[ExIdKeyDict]) -> ExIdKeyData:
+    return ExIdKey_Native(**kwargs)
+
+
+def pack_ExIdKey(key_data: ExIdKeyCompatible) -> ExIdKeyData:
+    if isinstance(key_data, tuple):
+        # SYNC:ExIdKey:Properties
+        return ExIdKey_Native(wikidata_prop=key_data[0], key_name=key_data[1])
+    if isinstance(key_data, dict):
+        return ExIdKey_Native(**key_data)
+    return key_data
+
+
+class ExIdKey_Columns(ExIdKeyData):
+    """implementer of ExIdKeyProto for Pony tables"""
+
+    # SYNC:ExIdKey:Properties
+    wikidata_prop: bool = orm.Required(bool)
+    """
+    `True` if key_name is a wikidata property,
+    `False` if key_name is a canonical key name.
+    """
+    key_name: str = orm.Required(str)
+    """
+    key name for external identifier
+
+    Should be used externally.
+    Should be unique worldwide, but one per external identifier.
+
+    Can either be a Wikidata property id (starting with `P`),
+    otherwise a canonical key names (see `docs/canonical_exids.md`).
+    """
+    orm.composite_key(wikidata_prop, key_name)
+
+    @classmethod
+    def get_by_data(cls: Type[T], key_data: ExIdKeyCompatible) -> Optional[T]:
+        d = pack_ExIdKey(key_data)
+        # SYNC:ExIdKey:Properties
+        return cls.get(
+            wikidata_prop=d.wikidata_prop,
+            key_name=d.key_name,
+        )
+
+    def update_from_key_map(self, key_data: ExIdKeyCompatible) -> bool:
+        data = pack_ExIdKey(key_data=key_data)
+        if not self.needs_update(key_data=data):
+            return False
+        # SYNC:ExIdKey:Properties
+        self.wikidata_prop = data.wikidata_prop
+        self.key_name = data.key_name
+        return True
+
+    def needs_update(self, key_data: ExIdKeyCompatible) -> bool:
+        data = pack_ExIdKey(key_data=key_data)
+        # SYNC:ExIdKey:Properties
+        return any(
+            (
+                self.wikidata_prop == data.wikidata_prop,
+                self.key_name == data.key_name,
+            )
+        )