[Design] Re: Design Digest, Vol 29, Issue 4

[Andi Vajda]

> Philippe Bossut wrote:

> (a) modify the item attributes so that it will appear in the collection
> as a result of the query
> - or -
> (b) be added to the collection as a specific inclusion

This is quite easy to implement. For an item to be explicitely added to a 
collection, that collection has to implement an 'add' method. On the 
Collection base class, 'add' is not implemented since most collections are 
based off abstract sets, that is, they are computed and that conflicts with 
explicitely 'add'ing items.

For example, for an item to appear in a KindCollection, it has to be made in 
that kind (or changed to it via stamping).

The InclusionExclusionCollection class, however, does implement 'add' and 
'remove'. With that implementation, it can decide whether to force an 
attribute value to fit a filter expression or whether to append the item to 
its inclusions ListCollection, bypassing the filter.

Andi..