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Consider modeling your problem into a rich Domain Model before trying to
apply DDD building-block concepts to it. In other words, apply DDD
practice to your domain problem, instead of trying to fit your domain
problem to a particular technology, architecture or pattern, e.g. DDD
aggregates, domain events, entities, value objects and domain services.<br><br>It's generally a mistake to base
your solution on the consistency/concurrency relationships between
domain concepts, and assume they are of one type (eventual?). Are we
still chasing silver bullets? Instead, you should consider each
consistency/concurrency relationships in terms of each collaboration
between objects within the business scenario.<br><br>I don't want to
write a long answer about how to specifically model your domain
problem. I leave it to you to ask if you want specific help, but a few
points to start you going. Note, there are no "sub-entities" as you put
it. ...<br><br>1. Consider what activities need to be recorded for business or legal reason. These <span style="font-style:italic;"><span>business </span></span><span style="font-style:italic;">transactions </span>are
the foundation of the business and your model. If the power fails,
have paper forms that represent them. In your case consider <span style="font-weight:bold;">Order</span>, <span style="font-weight:bold;">CallOff</span>, <span style="font-weight:bold;">GoodIssueRequest</span>.
These are modeled in a transaction-subsequentTransaction pattern.
SubsequentTransactions are created by the transaction that precedes
them. You did mention <span style="font-weight:bold;">ActualCallOff</span>, but I do not understand from your writing if this is actually a transaction.<br><br>2.
Recorded activities (transactions) interact with <span style="font-style:italic;">Things </span>and <span style="font-style:italic;">Parties </span>at <span style="font-style:italic;">Places</span>. It's true that typically one interacts with many Things,
(modeled as transaction-lineItems), but not necessarily. One
transaction can be associated with a single thing - like in your case an
<span style="font-weight:bold;">Order </span>is associated with an <span style="font-weight:bold;">Item</span>.<br><br>3.
When you have a specific item, model the set of all of them
explicitly. Don't leave it to a Repository alone to represent the set of
Items. Now in your model you have a place to evaluate, assess and
calculate aspects of your Items, i.e. <span style="font-weight:bold;">ItemDescription</span>. This way your model can become a self-contained <span style="font-style:italic;">working </span>model.<br><br>4.
You need to group Orders by number arbitrarily. At least that is my
understanding from your writing. In a domain model, we really only need
3 patterns to represent aggregate things <span style="font-style:italic;">- containment</span>, <span style="font-style:italic;">classification </span>and<span style="font-style:italic;"> part-of</span> an assembly. I would use the first of these to represent that Orders can be associated with an Order "number", i.e. an <span style="font-weight:bold;">OrderGroup.</span><br><br>5.
You mention a constraint - a business-rule. These should be in your
domain model. They are of 2 types:- <span style="font-style:italic;">property</span> rules and <span style="font-style:italic;">collaboration
</span>rules. Write a collaboration rule between the
transaction-subsequentTransaction objects mentioned in 1 above - <span style="font-weight:bold;">Order</span>-<span style="font-weight:bold;">CallOff.</span><span> The rule is tested when adding a CallOff to the Order.<br><br>I
wanted to try to show the start of another way here. Produce a domain
model, forget persistence and UI, and run the model by tests. For the
simple domain you describe, one could be demonstrating and clarifying a working model
in a few days to domain experts. Best of all, you now have a valuable business asset - a working model of your problem in business terms.<br><br>Best regards,<br>Aryeh<br><br></span>
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