Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]
Date: Thu, 16 Jun 2005 18:18:12 GMT
>> >> Are you sure you are not talking about the (rather old) idea that is >> commonly known as "the universal relation assumption" or "the >> universal-relation data model"? For a few references see:
> I find the problems raised in UR model very similar to those motivating
> COM. However, the provided solution is hardly acceptable (it is
> typcially relational). In COM we have advantages of UR model but the
> solution is based on other principles.
Yes, you also seem to have added a little frame logic (e.g. see F-logic) and concept lattices into the mix. Both are well-known and useful theories, but hardly replacements of the relational model. For references:
Moreover, these don't really solve the fundamental problem of the UR approach, which very much seems to be the backbone of your proposal, and therefore you have the same problems.
> select office_id
> from Offices
> where Managers.name = 'sally'
> is one of the things we want to automate in COM and this query has a a
> natural solution in COM.
Indeed. But this seems pretty much the only concrete improvement that you have demonstrated and it wasn't really much of a problem in the RM to begin with. Moreover, you have demonstrated in this newsgroup very convincingly that this comes at the price of a data model that is very hard to explain properly, even to experts in the field. That looks more like a step back then a step forward.
> Here are some differences between these two approaches:
> - COM is based haavily on dimension/subdimension duality for data access
> - COM uses concept graph with top and bottom concepts for representing
> syntax and semantics of data
> - COM defines its own basic interpretation of data: an item is
> group/category for its subitems; an item is a dimension value for its
> subitems; an item is a relation instance for its superitems (and some
> other basic interpetations). This changes the modelling approach itself.
> - COM defines its own general principles like what data is, how data is
> interpeted and so on, which are important not only for data modeling
> (and probably not so for data modeling) but are used for the next
> generation concept-oriented programming paradigm.
I've seen literally hundreds of articles with new proposals that made similar suggestions and claims, and which are now rightfully forgotten. Unless you show us a wide range of concrete examples where your data model really makes things simpeler, this just remains empty marketing speak.
- Jan Hidders