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    <p>The UML spec is incoherent regarding the aggregation vs. composition definitions. They are not properly defined, as has been shown by several authors (Henderson-Sellers among others). I suggest you don't waste your time trying to determine whether something in your mind maps best to one or the other. There is no right answer. :-)</p> <p>Myself, I often use an abstract whole/part relationship to model wholes and parts. Semantics about binding, lifetime and exclusivity can be given by pseudocode or annotations. There are so many different cases and scenarios that trying to foresee all the possibilities beforehand is not worth it. <strong>Edit</strong>: this approach was proposed by Henderson-Sellers and myself to OMG during the review round of an earlier version of UML, a few years ago. Unfortunately, it didn't make it. :-)</p> <p>Even if UML were coherent, there are not right or wrong models; some models are useful and some are not. You <em>create</em> models depending on the purpose you pursue.</p>
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    1. COThanks for your reply CesarGon. Yeah I did read in a UML book that one should not lose any sleep over whether to use Aggregation or composition - the book just said default to aggregation, and change it latter, i forgot about that. This whole designing before coding is really new to me. One thing though, what do you mean by abstract whole/part relationship? Do you mean you create an abstract class and have specialized classes inherit from it? Or is it more than that? I googled it but did not find a clear definition. Thanks again
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    2. COMuch simpler than that. I mean just use a "white diamond" shape meaning "whole/part relationship", without caring whether it's an aggregation or a composition. After all, "aggregation" and "composition" are meaningless mumbo-jumbo in UML. They lack a solid definition and as soon as you try to formalise their meanings, you find serious inconsistencies. So stick with something simpler, like "whole/part", which is enough to capture the semantics of most situations you will find around you. As I said, you can complete this with annotations where necessary for extra details.
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    3. COOk great, thanks. One more thing, do you know of any sites that focus on designing code or sites for people who like to look at well designed code or code designs? I think this will help me a lot if I can read how much more experienced people than me code
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