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Re: an XQuery API for Java

• To: Michael Kay <michael.h.kay@n...>
• Subject: Re: an XQuery API for Java
• From: Burak Emir <Burak.Emir@e...>
• Date: Tue, 06 Jul 2004 15:10:18 +0200
• Cc: xml-dev@l...
• In-reply-to: <20040706110848.XHKJ21846.mta08-svc.ntlworld.com@Turtle>
• References: <20040706110848.XHKJ21846.mta08-svc.ntlworld.com@Turtle>
• User-agent: Mozilla Thunderbird 0.5 (X11/20040208)

Michael Kay wrote:

>>Does the use of SequenceIterator imply that the result is 
>>materialized 
>>in memory, excluding delayed execution ?
>>Couldn't there be an implementation of the interface that just defers 
>>execution ?
>>    
>>
>
>The list underpinning the SequenceIterator isn't materialized, but if there
>are nodes in the sequence, then the trees rooted at these nodes are
>materialized. It's possible in theory of course to have a Node
>implementation that does deferred materialization, but Saxon doesn't do this
>currently.
>
>  
>
>>For document transformations, I think a JAXP result does not 
>>help much 
>>either - because if I understood it correctly, it can only be 
>>used for 
>>the "last step" - you cannot run queries or transformations.
>>    
>>
>
>Actually, one of the nice features of the JAXP interface (which appears not
>to have been studied closely by the XQJ designers) is the way it allows
>transformations to be pipelined.
>  
>
It is consistent with what you can do with queries in JDBC - even though 
every database system allows you to query the results of a query, in 
JDBC something like this is not considered useful - it's a kind of 
"design schizophrenia".

BTW, does JAXP make use of http://www.w3.org/TR/xml-pipeline/ (same 
question for Saxon) ? It must be pretty straightforward to put the name 
of a class in the "definition" attribute of the processdef element and 
then instantiate the transformers using Java's reflection mechanism.

It seems the same mechanism could apply to XQuery, if one replaces 
"Transformers" by subclasses of "XQueryExpression".

>In XSLT of course the question of how a stylesheet is supplied to the
>interface has an obvious answer: it is supplied as an XML document, using
>any representation of an XML document that one chooses.
>
>  
>
... and since XML is structured (not only by tags but also by 
namespaces), this allow to do a whole range of things that you cannot do 
on strings.

But it seems that XQueryX is not a very lean "tagification" of the 
non-XML XQuery syntax, using too many elements and too little 
attributes. And most of all, people do not seem to be used to dealing 
with computational objects like queries and stylesheets in programming 
languages.

cheers,
Burak

• References:
  • RE: an XQuery API for Java
    • From: "Michael Kay" <michael.h.kay@n...>

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