* Shane Hathaway <shane@zope.com> [2003-05-02 18:47]:
Well, perhaps I am incorrect in my thinking, but every discussion I can Google (heh, I finally used Google as a verb) that mentions both the entity-relationship model and the relational model explains it differently. First they introduce ERM then explain how to implement it using relations in a relational database. ERM seems to be described as the underlying model for relations.
There are a few places that mix the use of relation and relationship. In some contexts, the two words are synonyms, and it seems like some authors use both words loosely. I'd be happy to be proven wrong (so I can agree with you.) Is there a model that defines "relationship" as the concrete form of "relation", as you explained it? It seems to be the other way around. :-)
I don't think there is a model that defines relationship as I've explained it, I was merely thinking of the definition of the words "relation" and "relationship". I am happy to stick with "relationship" if "relation" is confused with its use in existing theory.
Iow, Relationship should subclass ComputedAttribute? I tried something like that but ran into some problems and just wanted to get something out there for comment.
Ok.
As a matter of interest how will get a handle on the instance if you subclass ComputedAttribute and don't initialise it with a function of the class where the Relationship is created? -- Roché Compaan Upfront Systems http://www.upfrontsystems.co.za