diff --git a/human_machine/trust_model.py b/human_machine/trust_model.py
index ad35e5a..d11d489 100644
--- a/human_machine/trust_model.py
+++ b/human_machine/trust_model.py
@@ -1 +1,61 @@
-print("Hello World")
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Dict
+
+@dataclass
+class TrustModel:
+    """
+    Represents a trust score for a user.
+
+    Attributes
+    ----------
+    user_id : str
+        Identifier for the user.
+    score : float
+        The accumulated trust score.
+    """
+    user_id: str
+    score: float = 0.0
+
+class TrustEvaluator:
+    """
+    Maintains and updates trust scores for users based on interactions.
+    """
+    def __init__(self) -> None:
+        self._models: Dict[str, TrustModel] = {}
+
+    def update(self, user_id: str, delta: float) -> TrustModel:
+        """
+        Update the trust score for a user.
+
+        Parameters
+        ----------
+        user_id : str
+            Identifier for the user.
+        delta : float
+            Amount to adjust the trust score (positive or negative).
+
+        Returns
+        -------
+        TrustModel
+            The updated trust model for the user.
+        """
+        model = self._models.get(user_id)
+        if model is None:
+            model = TrustModel(user_id=user_id)
+            self._models[user_id] = model
+        model.score += delta
+        return model
+
+    def get_score(self, user_id: str) -> float:
+        """Return the current trust score for the given user."""
+        return self._models.get(user_id, TrustModel(user_id)).score
+
+if __name__ == "__main__":
+    evaluator = TrustEvaluator()
+    evaluator.update("alice", 0.5)
+    evaluator.update("bob", -0.3)
+    evaluator.update("alice", 0.2)
+    print(evaluator.get_score("alice"))
+    print(evaluator.get_score("bob"))