Hi!

It's not direct squeak related, but may some experienced
programmers know how to "do it the right way(tm)"?

>From http://swiki.squeakfoundation.org/sea/90:
______________________________
I'm thinking about using an OODB as the persistence layer. Why? Because I
won't have to duplicate class hierachy and behaviour in the database and the
logic. 
The two most complicated things in the database are assemblies and the print
output. 
There are two types of assembles: an assembly and a subassembly. Theses have
to be editable. An order usually is an order for an assembly, but it don't
have to. The assembly could "evolve" due to changes made to a machine, where
the assembly is a part of. So, an assembly must be versioned, and editing an
assembly have to result in a copy with a new version if the assembly is
referenced anywhere in the system.
Sometimes, an assembly is of no use anymore (if it is not referenced in an
order, i.e. it was a version temporary between two edits). It then should be
"garbage collected". 
I think this could be implemented best using a OODB. 

The implementation using an OODB leads to another problem: How do you ensure
some constraints? For example, if you have a supplier for an article (being
used in an assembly), you should ensure that on cannot delete a used
(referenced) address out of the addresses collection. There are more constraints
here, like ensure that article numbers are only used once in the collection of
articles. 
A possibility is to subclass the used collection class. So if I want to
introduce some constraints for articles, I subclass OrderedCollection,
introducing an ArticleCollection. In the #add: and remove:# methods, I check my
constraints. But I think there is a better way :-)
______________________________

So is subclassing OrderedCollection the right way? Or should
I solve the problem using another solution (maybe a 
ConstrainedCollection which stores it's constraints as blocks)?

Kind regards, Markus

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