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Re: [xml-dev] Converting a variety of data formats, containingvarious kinds of data into a common intermediate form

Trying to think of some context that might make the statement less bogus... lets be charitable and assume the best!

I guess what they are saying is we always have to write the n converters, but with RDF you dont need to then write the loader to the data store from that format (or the database schema). (And perhaps that converting to rdf is relatively easy??)  By the time you make a highly generic universal schema that works by annotation rather than named structures, and you allow all sorts of ordering and set etc possibilities, you probably end up with something like RDF anyway, so why bother?

So why would it be less computationally expensive/hard/intractable? 

I am tempted to guess that a contrast is being drawn between between supporting large kitchen sink schemas (often favoured by markup people) and supporting generic schemas (often favoured by ETL people.)  That is definitely a real issue, one that impacts me every day at my current (soon to be former) employer.

Mainstream XML technology definitely disfavours generic approaches: to move to generic approaches where the specific semantics is in attributes *and* retaining validation requires moving to RELAX NG or Schematron in which attributes are first-class citizens (rather than dtds or xsd where all patterns/types are keyed by element context only.) 

Even Xpath's syntax disfavours generic approaches (by providing no support), no crIticism implied. I have been working with generic schemas for much of the last decade, and I really think XSL T Xpath would be enhanced by providing some simple macro system to uncomplicate paths: for example  so that instead of writing


i could declare a virtual child named birthday-event with that xpath, and then use a virtual axis:


(And yes I know i can use functions. If you really think functions are equivalent syntactical sugar, consider why xpath syntax does not just use function syntax for axes in the first place...)

So those kind of reasons (easy loading of rdf, clumsy support for highly generic schemas in xsd/xpath/xquery) may indeed make RDF attractive for some important classes of n:1 projects. It is not unthinkable.

Rick Jelliffe

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