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[Bug 2753] wd-27: Errors in component diagram

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Date: Tue, 08 Jan 2008 09:48:31 +0000
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To: www-xml-schema-comments@w3.org
Message-Id: <E1JCB4R-0007fq-Sx@wiggum.w3.org>

http://www.w3.org/Bugs/Public/show_bug.cgi?id=2753





------- Comment #3 from mike@saxonica.com  2008-01-08 09:48 -------
The diagram is clearly intended to be a "UML Class Diagram", for which you can
find a tutorial at
http://www.sparxsystems.com.au/resources/uml2_tutorial/uml2_classdiagram.html
(The actual specification can be reached via www.uml.org, but the PDF file
crashes Firefox on my machine).

I think the dashed line has been made dashed purely because it has a crossover
with solid lines; there are no semantics intended.

All the arrows on the diagram are shown as "aggregation" relationships. I think
many UML users tend to show all 1-to-many associations as aggregation
relationships simply because the notation is more graphic; in fact I have never
understood the distinction UML tries to make between aggregations and more
general associations; it seems to be entirely subjective.

One could certainly question the analysis: for example element-declaration
should not have separate relationships with simple-type-definition and
complex-type-definition, it should have a single relationship with
type-definition, which should exist as a generalisation of simple-type and
complex-type. This one is clearly a many-to-many relationship, and although I
think it's legal in UML, I personally find the notion of modelling a
many-to-many relationship as an aggregation pretty weird.
Received on Tuesday, 8 January 2008 09:48:33 GMT

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