--- a
+++ b/annotations.py
@@ -0,0 +1,160 @@
+from typing import List, Tuple, Optional
+
+
+class Annotation:
+    """
+    A generic class for annotations
+    """
+
+    def __init__(self, ann_id: str, ann_name: str = None) -> None:
+        self.ann_id = ann_id
+        self.name = ann_name
+
+
+class Entity(Annotation):
+    """
+    Objects that represent named entities
+    """
+
+    def __init__(self, entity_id: str,
+                 entity_type: str = None,
+                 char_range: List[int] = None) -> None:
+        """
+        Initializes Entity object.
+
+        Parameters
+        ----------
+        entity_id : str
+            Unique entity ID.
+        entity_type : str, optional
+            The type of entity. The default is None.
+
+        """
+        super().__init__(entity_id, entity_type)
+        if char_range is None:
+            self.range = [None, None]
+        else:
+            self.range: List[int] = char_range
+        self.ann_text: str = ""
+        self.relation_group: str = ""
+
+    def set_range(self, new_range: List[int]) -> None:
+        """
+        Add annotation range
+        """
+        self.range = new_range
+
+    def set_text(self, text: str) -> None:
+        """
+        Sets the annotation text
+        """
+        self.ann_text = text
+
+    def set_entity_type(self, entity_type: str) -> None:
+        """
+        Sets the entity type
+        """
+        self.name = entity_type
+
+    def __repr__(self) -> str:
+        """
+        String representation of the object
+        """
+        string = "\n"
+        string += "ID: " + self.ann_id + "\n"
+        string += "Entity name: " + str(self.name) + "\n"
+
+        string += "Character range: "
+        string += str(self.range[0]) + " " + str(self.range[1]) + "\n"
+
+        if self.ann_text:
+            string += "Entity text: '" + str(self.ann_text) + "'"
+
+        return string
+
+    def __str__(self) -> str:
+        return self.__repr__()
+
+    def __getitem__(self, key: int) -> int:
+        """
+        Makes the class subsriptable on range
+        """
+        return self.range[key]
+
+    def __iter__(self) -> Tuple[int, int]:
+        """
+        Makes class iterable on range
+        """
+        yield self.range[0]
+        yield self.range[1]
+
+    def __eq__(self, other) -> bool:
+        """
+        Overrides equality method
+        """
+        if self.name == other.name and self.range == other.range:
+            return True
+        else:
+            return False
+
+
+class Relation(Annotation):
+    """
+    Objects that represent relations between named entities
+    """
+
+    def __init__(self, relation_id: str, relation_type: str,
+                 arg1: Entity = None, arg2: Entity = None) -> None:
+
+        super().__init__(relation_id, relation_type)
+        self.arg1 = arg1
+        self.arg2 = arg2
+
+    def set_entity_relation(self, arg1: str, arg2: str) -> None:
+        """
+        Sets the entities that are related
+        """
+        self.arg1 = arg1
+        self.arg2 = arg2
+
+    def get_entities(self) -> List[Optional[Entity]]:
+        """
+        Returns related entities
+        """
+        return [self.arg1, self.arg2]
+
+    def set_relation_type(self, relation_type: str) -> None:
+        """
+        Sets the relation type
+        """
+        self.name = relation_type
+
+    def __repr__(self) -> str:
+        """
+        String representation of the object
+        """
+        string = "\n"
+        string += "ID: " + str(self.ann_id) + "\n"
+        string += "Relation type: " + str(self.name) + "\n"
+        string += "\nEntity 1: \n"
+        string += self.arg1.__repr__() + "\n"
+        string += "\nEntity 2: \n"
+        string += self.arg2.__repr__()
+
+        return string
+
+    def __str__(self) -> str:
+        return self.__repr__()
+
+    def __eq__(self, other) -> bool:
+        """
+        Overrides the default equality method.
+        """
+        if self.arg1 == other.arg1 and self.arg2 == other.arg2:
+            return True
+
+        elif self.arg2 == other.arg1 and self.arg1 == other.arg2:
+            return True
+
+        else:
+            return False