1. Entity vs Datatype

2. IPR Declaration Is there any IPR associated with this presentation NO
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3. OMG UML Specification
“A DataType is a kind of Classifier. DataType differs from Class in that instances of a DataType are identified only by their value. All instances of a DataType with the same value are considered to be equal instances. If a DataType has attributes (i.e., Properties owned by it and in its namespace) it is called a structured DataType. Instances of a structured DataType contain attribute values matching its attributes. Instances of a structured DataType are considered to be equal if and only if the structure is the same and the values of the corresponding attributes are equal.”

4. DDD Entity vs Datatype Summary
Characteristic
Entity
Datatype
Mutability
Mutable attribute values
Immutable attribute values
Identity
Immutable identifier added
(Immutable) Attribute values #
Equality
Compare (immutable) identifier values
Compare (immutable) attribute values #
Uniqueness
Unique identifier means every Entity can be distinguished
Many datatypes may have the same attribute values and hence there is no real notion of uniqueness
Changing an attribute value
mutate in place
create a new datatype with the required value and update the reference to point to it
Valid as an Entity attribute type No
Yes
Valid as a Datatype attribute type
Can be linked via associations
Not incoming to a Datatype. Outgoing from a Datatype is possible to an Entity
# - the default would be for every attribute value to be part of the identity. In some cases attributes such as descriptions may be excluded by explicitly defining which attributes form the identity