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   Re: [xml-dev] Seeking Examples of XSLT Memory Stress

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  • To: Michael Kay <mike@saxonica.com>
  • Subject: Re: [xml-dev] Seeking Examples of XSLT Memory Stress
  • From: Bob Foster <bob@objfac.com>
  • Date: Wed, 17 Aug 2005 15:57:03 -0700
  • Cc: xml-dev@lists.xml.org
  • In-reply-to: <20050817175530.8C0A82FD78@loot.dreamhost.com>
  • References: <20050817175530.8C0A82FD78@loot.dreamhost.com>
  • User-agent: Mozilla Thunderbird 1.0.2 (Windows/20050317)

But then the semantics of unload are that those two guarantees no longer 
apply. Is that too hard to specify?

Bob Foster

Michael Kay wrote:
>>If the document falls out of scope then both XSLT 1 and 2 allow
>>an implementation to discard it.  I don't think we'll see a
>>procedural way to discard a document otherwise, except as
>>part of something like the XQuery update facility perhaps.
> In practice it's quite difficult to discard the document automatically. The
> spec offers two guarantees:
> (a) if the same document (URI) is loaded again, you'll get the same node
> identifiers
> (b) if the same document (URI) is loaded again, it will have the same
> content
> It would be possible to discard the document and achieve (a) by remembering
> the node identifiers and reusing them if needed. Achieving (b) though is
> really hard, given that the URI might in the worst case identify a random
> number generator. The only real way to do it is to serialize a private copy
> of the document to disk.
> The real problem though is in deciding when it's a good idea to discard the
> document. For example, if the stylesheet is working its way through the
> @href links from the primary source document, what's the chance that you'll
> want to visit the same target document more than once? That's why I decided
> that in this case having a user function to tell me when the document is no
> longer needed is rather more useful.
> Michael Kay
> http://www.saxonica.com/


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