Re: couple of spec comments

Jonathan,

in case of external functions the analogy for me is
EJB, or any other deployable J2EE artifact. Initially
there were no standard deployment descriptors, which
made porting EJBs from one WAS to another quite
challenging (not that it's a cake now, but it's
certainly better than it used to be). Same with XQuery
implementations: standardizing "deployment
descriptors" for external functions would provide at
least some level of portability.

Cheers

Vadim

--- Jonathan Robie <jonathan.robie@softwareag.com>
wrote:
> At 10:23 AM 12/27/2001 -0800, Vadim Draluk wrote:
> >Hi,
> >
> >here are my initial 2c on the new XQuery/XPath
> specs.
> >
> >1. External functions, mentioned in issues 124 and
> >223, is a very important feature indeed. However it
> >would be insufficient simply to define them as
> >outlined in 223. The invocation paradigm has also
> to
> >be addressed somehow: system library function, Java
> >class, EJB or COM interface method, SOAP invocation
> >etc, just to name some possibilities.
> 
> The rest of XQuery is not defined in terms of the
> software used to realize 
> it. Why should this be different for external
> functions? I think there is a 
> real advantage to saying that an implementation may
> implement external 
> functions any way it chooses, while still providing
> function prototypes 
> that give the type information to the query
> processor.
> 
> Naturally, implementations will have to provide a
> way of making external 
> functions available. But does that need to be
> specified in the standard?
> 
> >2. Recursion in dereferencing. As I understand it
> such
> >recursion is not allowed, unlike one over
> conventional
> >navigation axes. So the manager-employee example in
> >2.3.3 could not be generalized, say, to look for a
> >person some place up the reporting chain. This
> could
> >become more conspicuous an omission if
> dereferencing
> >syntax is merged with one of axes, as considered in
> >227.
> >
> >The recursion in question can become very useful,
> for
> >example, for advanced UDDI registry querying,
> allowing
> >to traverse tModel hierarchies.
> 
> I certainly understand why you would think that.
> There are some important 
> concerns for recursion in references, though. One is
> that references on the 
> World Wide Web can create very large networks, with
> high latency times, and 
> dreadful consequences for performance. Recursive
> traversal of references is 
> unlikely to be well optimized in the general case.
> 
> Given that, using recursive functions for traversing
> references seems to 
> work pretty well. This is a strategy I have used
> successfully for both RDF 
> and Topic Maps - see the following paper:
> 
>
http://www.idealliance.org/papers/xml2001/papers/html/03-01-04.html
> 
> 
> These are my opinions right now. They may be quite
> different from the 
> opinions of Software AG, the W3C XML Query Working
> Group, or the opinions 
> that I will have after reading and considering your
> response.
> 


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Received on Friday, 11 January 2002 17:18:03 UTC