Here at RubyTapas we have been searching for a good definition or discussion of entity, as the term is used in the context of domain driven design.  So far the best we have found is —

“An object fundamentally defined not by its attributes, but by a thread of continuity and identity.”

— in the DDD Community Glossary of Domain-Driven Design Terms.

Wikipedia explains further with an example:

Most airlines distinguish each seat uniquely on every flight. Each seat is an entity in this context. However, Southwest Airlines, EasyJet and Ryanair do not distinguish between every seat; all seats are the same. In this context, a seat is actually a value object.

Paul Rayner has a discussion of “Aggregates & Entities in Domain-Driven Design” in his “Leading by Design” blog.

Joe Ocampo has a discussion of Entities in Domain Driven Design at Los Techies.


The Masala Chef wonders if the Head Chef might make a sideboard, or even an episode, on “Entity“, so if you want to nag us to supply better definition and/or discussion of entities, or if you want to suggest any other online references explaining “entity”  (within the context of domain driven design), please submit the form below. Thanks!

— K. A. G. Sundaram,  Masala Chef

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