XML query engines: was RE: Is XML dead already or what?

len bullard cbullard at hiwaay.net
Sun Jan 31 21:27:54 GMT 1999

Borden, Jonathan wrote:
>My personal opinion is
> that it is a hybrid relational and 'object' database approach.

I don't think this could be disputed easily or without resort to 
specialized application requirements.  It has been done like this 
in many apps for many years.  That is why these threads look 
odd to me.  IOW, it is already best practice.  I don't think 
there is a rule, but a rule of thumb is to manage fragments 
relationally and even author that way, and to package in objects 
for distribution.  It is also very very cheap and works right 
now with cheap COTS products and no reeducation of the 
production staff or the users.

I guess what is in question is if object management 
stands up well on the production and server side.  Otherwise, 
packaging and sending SQL queries and getting links, objects 
or files back is already effective.  It might be more interesting 
to know what requirements there are for more than that.

 > The problem with a straight relational approach is that we need to
> containment and heirarchies... in SQL terms this means joins, perhaps
> multilevel joins when documents are deep.

True.  HTML works remarkably well for assembling fragments precisely 
because it is so flat.  Let me compare this to a DTD that was deeply 
nested, recursive, etc.  MIL-D-87269 - IETM DB.  When delivered out 
of a relational db, it was quite a chore to reuse it outside the 
viewer designed for the delivery.  The problem was chasing the 
references to work out how to assemble it.   It was doable but it 
took negotiation of the commuicating parties above and beyond 
the 87269 spec.  That was why the US Navy MID project was 
done:  to create a view package for deliverables.

Modeling the hierachies and containment isn't that hard.   Typically, 
filtering it back into a relational db and using SQL works.  That 
is my point about the rough symmetry of functionality between 
queries, script logic, and DTDs.  Which would you rather 
manage or try to standardize for an enterprise?

len bullard

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