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> At least with the implementations I am familiar with, natvie
> XML dbs do their own version of shredding. Randomly
> accessing XML document contents efficiently requires this.
> Now, their implementations are optimized for XML, an
> important difference from relational approaches, but their
> storage image is far from document form.
I think it's a little far-fetched to treat as equivalent a system with an
internal data structure designed specifically as an implementation of the
hierarchical XML data model, and a system that constructs a tabular
representation using a data model that was never even designed to enable
recursive queries. If you've ever had a corridor conversation with someone
trying to implement mixed content or comments and PIs or namespaces in a
shredded table, you can only feel sorry for the guy.
> And, of course, they don't have to be as good at it as a
> native XML DB. They just have to be good enough.
Here you are certainly right. A new database technology, operating system,
or programming language has to be rather special to displace the established
30-year-old stuff that most of us work with.
But I once thought that C would never be displaced, and overnight Java came
along and everyone decided it was the next thing. I don't know why it
happens, but sometimes the industry decides to take a step forwards.