When should we use weak entities when modelling a database?

Posted by Songo on Programmers See other posts from Programmers or by Songo
Published on 2012-12-06T11:32:05Z Indexed on 2012/12/06 17:21 UTC
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This is basically a question about what are weak entities? When should we use them? How should they be modeled?

What is the main difference between normal entities and weak entities? Does weak entities correspond to value objects when doing Domain Driven Design?

To help keep the question on topic here is an example taken from Wikipedia that people can use to answer these question: enter image description here

In this example OrderItem was modeled as a weak entity, but I can't understand why it can't be modeled as a normal entity.
Another question is what if I want to track the order history (i.e. the changes in it status) would that be a normal or weak entity?

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