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    <p>Wonder if you're mis-interpreting the guidance around aggregate roots (Or maybe I did...).</p> <p>I never read the guidance as saying: "the aggregate must provide proxy methods for every conceivable property of all its aggregated objects". Rather, I think it says: "the aggregate controls the lifecycle, identity and relationships of its aggregated objects". </p> <p>So it's perfectly valid for a client to ask the aggregate for a (transient) reference to one of its objects and do something with it. I don't have my copy of DDD here to confirm the wording, but that would seem consistent with the <a href="http://www.infoq.com/resource/minibooks/domain-driven-design-quickly/en/pdf/DomainDrivenDesignQuicklyOnline.pdf" rel="nofollow">DDD summary ebook</a> (p53) which says:</p> <blockquote> <p>It is possible for the root to pass transient references of internal objects to external ones, with the condition that the external objects do not hold the reference after the operation is finished.</p> </blockquote> <p>So, in your case clients would ask <code>MedicalReport</code> for instance(s) of <code>IMedicalNote</code>, get back subtypes, operate on them as appropriate and pass back to the root if applicable. </p> <p>As I say: can't say for sure that's in line with DDD, but common sense says it's a more scalable and flexible solution than trying to reflect every property/method of every subtype in the aggregate root.</p> <p>hth.</p>
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    1. POAccessing Subclassed Aggregate Members
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    1. COMy understanding is that you can retrieve the internal object (IMedicalNote) but only for readonly purpose. You're not supposed to make any modification to it. All modifications have to be made via the root so that it can control the integrity. Also, what do you mean by passing it back to the root? Once we modify the property of the child externally, then that's it, it's changed (by reference), bypassing the root, isnt it? What does "passing back to the root" do exactly?
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    2. COApologies, answer somewhat ambiguous. Root passes back copies of the objects which client then updates and passes back to root. Root then responsible for checking invariants & setting up relationships. Provides a sensible split of responsibility: root knows about relationships and constraints among aggregated objects but doesn't need to know details of all subtypes. Clients can operate on specific subtypes as required. Note Root might need to know some subtype details (e.g. if it must hold exactly one `BloodCheckNote` but could have many `TemperatureNote`s).
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    3. COYou mean to create a clone mechanism so that the root will always pass back a clone of each child-note when accessed via root's public getter? And then a way to copy these values back to its actual object once the client return these children back to the root. Just wanted to clarify if thats what you meant, because it sounds like quite a bit of work. Cheers
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