Re: Re: aggregation and states



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From: Les Munday (baldrick@ureach.com)
Date: Thu 13 Jun 2002 - 19:48:24 BST


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---- On Thu, 13 Jun 2002, Ulf Schuenemann (ulf@cs.mun.ca) wrote:

> From the state modeling side, Harel (father of StateCharts) 
and Gery
> ["Executable Object Modeling with Statecharts" Computer 30(7) 
July
> 1997, early version in ICSE'96] are only concerned with 
composite
> objects.  They accept (weak) aggregation only for consistency 
with
> UML.  They describe the semantics of UML's aggregation (wrt. 
state
> modeling?) as being ``essentially just that of a special
> association.''  Preferable would be a more explicit statement 
like
> "aggregation is irrelevant to state modeling" (but maybe it 
isnt't?).
> [NB also for composition Harel+Gery do not mention 
constraints on states]
> 

And I agree. I was object modeling long before UML came on the 
scene and I had no special notation for aggregation nor 
composition.

As someone pointed out to me when I first discovered 
composition, 'is this not just a special type of association 
with a cardinality of exactly 1 on the "whole" end?'.

Les.

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