Domain object referenced by two Aggregate roots

i have designed a model for a website with the following domain objects:

Article <> Event <> (like festival, ...) Comment <> (can be created for articles and events)

Where do i put the Comment-Domain Object in the model? Should it stay alone or use it's own aggregate? But a comment makes no sense without an article or an event....

Thanks 开发者_开发百科Mario

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Firstly DDD doesn't prevent two aggregate roots to reference the same domain object. As long as the object is not part of both the aggregate root boundaries.

In this case I would consider to create an ArticleComment and EventComment objects, each belonging to their relevant aggregate roots. This should be clearer working with a comment object that only applies to one type being commented on. You can still enforce common data and behaviour by having an abstract Comment class.