diff --git a/pp2psdm/utils/__init__.py b/pp2psdm/utils/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/pp2psdm/utils/ext_entity_mapping.py b/pp2psdm/utils/ext_entity_mapping.py
new file mode 100644
index 0000000..4080d72
--- /dev/null
+++ b/pp2psdm/utils/ext_entity_mapping.py
@@ -0,0 +1,160 @@
+import os
+from dataclasses import dataclass
+from enum import Enum
+from pathlib import Path
+from typing import Type, Self, Union
+
+import pandas as pd
+from pandas import DataFrame
+
+from pypsdm import GridContainer, RawGridElementsEnum, SystemParticipantsEnum
+from pypsdm.io import utils
+from pypsdm.io.utils import read_csv, df_to_csv
+
+# todo: expand this later
+column_schemes: dict[Union[RawGridElementsEnum | SystemParticipantsEnum], str] = {
+    RawGridElementsEnum.NODE: "",
+
+    SystemParticipantsEnum.LOAD: "pq",
+    SystemParticipantsEnum.PHOTOVOLTAIC_POWER_PLANT: "p"
+}
+
+
+class DataTypeEnum(Enum):
+    EXT_PRIMARY_INPUT = "primary_input"
+    EXT_EM_INPUT = "em_input"
+    EXT_GRID_RESULT = "grid_result"
+    EXT_PARTICIPANT_RESULT = "participant_result"
+
+def _to_df(entries: list[(str, str,  str, DataTypeEnum)]):
+    entry_list = [{"uuid": entry[0], "id": entry[1], "column_scheme": entry[2], "data_type": entry[3].value} for entry in entries]
+
+    try:
+        return pd.DataFrame(entry_list).set_index("uuid")
+    except KeyError:
+        return pd.DataFrame(entry_list)
+
+@dataclass(frozen=False)
+class ExtEntityMapping:
+    data: DataFrame
+
+    @property
+    def uuid(self):
+        return self.data["uuid"]
+
+    @property
+    def id(self):
+        return self.data["id"]
+
+    @property
+    def column_scheme(self):
+        return self.data["column_scheme"]
+
+    @property
+    def data_type(self):
+        return self.data["data_type"]
+
+
+    def add_entry(self, uuid: str, external_id: str, column_scheme: str, data_type: DataTypeEnum):
+        field_to_value = {"uuid": uuid, "id": external_id, "column_scheme": column_scheme, "data_type": str(data_type.value)}
+        row = pd.DataFrame([field_to_value]).set_index("uuid")
+        return ExtEntityMapping(pd.concat([self.data, row], ignore_index=False))
+
+    def add_entries(self, entries: list[(str, str,  str, DataTypeEnum)]):
+        rows = _to_df(entries)
+        return ExtEntityMapping(pd.concat([self.data, rows], ignore_index=False))
+
+    def to_csv(self, path: str, mkdirs=False, delimiter: str = ","):
+        # local import to avoid circular imports
+
+        # Don't write empty entities
+        if not self:
+            return
+
+        data = self.data.copy()
+        df_to_csv(
+            data,
+            path,
+            self.get_file_name(),
+            mkdirs=mkdirs,
+            delimiter=delimiter,
+        )
+
+    @classmethod
+    def create_from_grid(
+            cls: Type[Self],
+            grid: GridContainer,
+            primary: list[SystemParticipantsEnum],
+            em: list[SystemParticipantsEnum],
+            result: list[Union[RawGridElementsEnum, SystemParticipantsEnum]]
+    ) -> Self:
+        primary_inputs = {asset: grid.get_with_enum(asset).uuid.to_list() for asset in primary}
+        em_inputs = {asset: grid.get_with_enum(asset).uuid.to_list() for asset in em}
+        result_outputs = {asset: grid.get_with_enum(asset).uuid.to_list() for asset in result}
+
+        return cls.from_grid(grid, primary_inputs, em_inputs, result_outputs)
+
+
+    @classmethod
+    def from_grid(
+            cls: Type[Self],
+            grid: GridContainer,
+            primary_inputs: dict[SystemParticipantsEnum, list[str]],
+            em_inputs: dict[SystemParticipantsEnum, list[str]],
+            result_outputs: dict[Union[RawGridElementsEnum, SystemParticipantsEnum], list[str]]
+    ) -> Self:
+        entries: list[(str, str,  str, DataTypeEnum)] = []
+
+        for asset, uuids in primary_inputs.items():
+            elements = grid.participants.get_with_enum(asset).data
+            column_scheme = column_schemes[asset]
+            entries += [(uuid, elements.loc[uuid]["id"], column_scheme, DataTypeEnum.EXT_PRIMARY_INPUT) for uuid in uuids]
+
+        for asset, uuids in em_inputs.items():
+            elements = grid.participants.get_with_enum(asset).data
+            entries += [(uuid, elements.loc[uuid]["id"], "p", DataTypeEnum.EXT_EM_INPUT) for uuid in uuids]
+
+        for result_asset, uuids in result_outputs.items():
+            elements = grid.get_with_enum(result_asset).data
+            data_type: DataTypeEnum
+
+            if isinstance(result_outputs, RawGridElementsEnum):
+                data_type = DataTypeEnum.EXT_GRID_RESULT
+            else:
+                data_type = DataTypeEnum.EXT_PARTICIPANT_RESULT
+
+            column_scheme = column_schemes[result_asset]
+            entries += [(uuid, elements.loc[uuid]["id"], column_scheme, data_type) for uuid in uuids]
+
+        return cls(_to_df(entries))
+
+
+    @classmethod
+    def from_csv(
+        cls: Type[Self],
+        path: str | Path,
+        delimiter: str | None = None,
+        must_exist: bool = True,
+    ) -> Self:
+        file_name = cls.get_file_name()
+
+        file_path = utils.get_file_path(path, file_name)
+        if os.path.exists(file_path):
+            return ExtEntityMapping(read_csv(path, file_name, delimiter).set_index("uuid"))
+        else:
+            if must_exist:
+                raise FileNotFoundError(f"File {file_path} does not exist.")
+            else:
+                return cls.create_empty()
+
+    @staticmethod
+    def get_file_name() -> str:
+        return f"ext_entity_mapping.csv"
+
+    @classmethod
+    def create_empty(cls: Type[Self]) -> Self:
+        """
+        Creates an empty instance of the corresponding entity class.
+        """
+        data = pd.DataFrame(columns=["uuid", "id", "column_scheme", "data_type"])
+        return cls(data)
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