Re: Dependencies and associations



Date view Thread view Subject view Author view

stuart kent (stuart@mclellankent.com)
Fri, 22 Jun 2001 17:42:18 +0100


I'd just like to support one of Daniel's comments, and my own comment to another. > 1. it's quite possible to interpret associations uniformly at different > stages. in the approach i teach, they always denote state and their > constraints denote state invariants. in object models of code, i admit the > _additional_ interpretation that an association represents a field, but the > notion of association as state component still holds. Exactly. I think it is quite possible for a meaning to be given to association at the analysis level which is consistent with that used in the design/implementation stages. For example, at design/implementation one would also like to be able to make the distinction that Daniel alludes to as to whether the association (or one end of it) is stored or calculated. Of course one is also free to define refinement mappings between models, so there may be an association at the abstract level which is refined to a whole collaboration of objects (possibly involving a number of associations) at the concrete level, but this is quite separate from the meaning of association. > 4. i quite agree that the confusion of two different design processes in > UML -- roughly the Booch vs. OMT approach -- is the root of many problems. > and i applaud your desire to match notations and semantics to method. that > said, i do think that it's desirable and possible to have notations that > have semantics and analyses that are independent of any method. we've tried > hard to achieve this independence with Alloy. This suggests that we should be striving to achieve overlap between languages where we can, so that commonality can be exploited e.g. in tools, but be prepared to also allow languages to specialise and extend the common part. For example, part of the common core of an OO analysis and design modelling language is association, but in the design modelling language one wishes to add the distinction of whether the ends of the association are calculated or stored. The challenge that the UML 2 RFP has set is to find a language definition architecture which supports the development of a family of languages along these lines. I think this is a difficult challenge. Any views on this? Stuart -- ukc home - http://www.cs.ukc.ac.uk/people/staff/sjhk sse research group @ ukc - http://www.cs.ukc.ac.uk/research/sse puml group - http://www.puml.org/


Date view Thread view Subject view Author view