SQL Server 2005

[Michael Kay]

> Interesting. I thought that reliance on a single process 
> model was why 
> hierarchical databases (largely) lost out to relational databases.

No, that's far too simple an analysis. The biggest factor was that
relational database products were engineered to be cross-platform, and came
around at the time when minicomputer architectures were starting to offer a
cost-effective alternative to the mainframe. They were also declarative
rather than procedural, which was a good idea at a time when hardware was
getting cheaper and people more expensive. The declarative/procedural
dimension is quite orthogonal to the relational/hierarchic dimension but the
two have often been confused. (People are still confused, because XQuery is
declarative and hierarchic, and they weren't taught that that was possible.)

It's true that process-model-neutrality was one of the selling points of
relational databases. But I don't think that's why people (eventually)
bought them. Most people bought them simply because the previous generation
of hierarchical and network products had failed to get their standards act
together.

But what I'm really saying here is that we shouldn't be so database-centric
in our thinking. The success of XML is because architectures are now built
around information interchange rather than information storage; storing the
stuff is secondary, and the database needs to adapt to that different world.

Michael Kay
http://www.saxonica.com/