Could I attempt a summary?
Firstly, as David C pointed out, for-each is not a loop. Think of it as
processing all the items in parallel, even if the implementation chooses to
do it sequentially.
Secondly, you're not allowed to read a document that was written earlier in
the transformation. That applies to doc-available() just as much as to
doc().
Thirdly, and this has also been said already, though perhaps not very
clearly: your problem description essentially says that you are eliminating
duplicates, and the right tools for that job in XSLT 2.0 are
distinct-values() and xsl:for-each-group.
Fourthly, your strategy doesn't work because doc-available() is defined to
be stable. Once you've called doc-available('abc.xml') and have received the
answer "false", the system is obliged to continue returning the answer false
if you call the function again with the same argument. [That's the way it is
supposed to work. To be honest, I'm pleasantly surprised Saxon is getting
this right, and I wouldn't guarantee that it will do so in all
circumstances!]
Michael Kay
http://www.saxonica.com/
-----Original Message-----
From: Duane Gran [mailto:dmg2n(_at_)virginia(_dot_)edu]
Sent: 02 May 2007 15:06
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
Subject: [xsl] loop timing and result-document flush
XSL experts,
I have an XSL which loops over a set of elements in search of
links and creates a result document for the link. In some
cases there is more than one link to the same anticipated
document, so I use the doc-
available() to test first for its existence before creating
the file. This is intended to avoid a DynamicError related
to writing more than one result document to the same URI.
However, when I run the program against a large set of
documents after 10 minutes or so I get the DynamicError.
Below is the output (run via ant) along with some debugging
fields I'll explain in a moment:
[xslt] test for doc /Users/dgran/dev/rose/build/zoom/
1-1861.wrenn.320-321.img.html available: false
[xslt] creating file: /Users/dgran/dev/rose/build/
zoom/1-1861.wrenn.320-321.img.html
[xslt] test for doc /Users/dgran/dev/rose/build/zoom/
1-1861.wrenn.320-321.img.html available: false
[xslt] creating file: /Users/dgran/dev/rose/build/
zoom/1-1861.wrenn.320-321.img.html
[xslt] Failed to process /Users/dgran/dev/rose/deploy.temporary/
1-1861.wrenn.rad.xml
BUILD FAILED
/Users/dgran/dev/rose/build.xml:395: The following error
occurred while executing this line:
/Users/dgran/dev/rose/build.xml:77: net.sf.saxon.trans.DynamicError:
Cannot write more than one result document to the same URI:
file:/ Users/dgran/dev/rose/build/zoom/1-1861.wrenn.320-321.img.html
In the first case, the file (1-1861.wrenn.320-321.img.html)
is correctly created because it doesn't exist yet. In the
second case the doc-available() method should return true and
skip the result- document command, but it fails to work. My
hypothesis is that the
result-document() method isn't finished flushing before the call to
doc-available() is made.
Assuming my guess is correct, is there a way in XSL to assure
that the document is finished writing before continuing to
the next iteration in the loop? Maybe there is another way
of skinning this cat. I welcome suggestions. I'm using
Saxon 8-7-3j. Below is a simplified version of my stylesheet:
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
version="2.0">
<xsl:template match="/">
<xsl:for-each select="ram|//repro|//page|//figure">
<xsl:variable name="zoomhtml">
<xsl:text>build/zoom/</xsl:text>
<xsl:value-of select="@image"/>
<xsl:text>.img.html</xsl:text>
</xsl:variable>
<xsl:message>
test for doc <xsl:value-of select="$zoomhtml"/> available:
<xsl:value-of select="doc-available($zoomhtml)"/>
</xsl:message>
<xsl:choose>
<xsl:when test="doc-available($zoomhtml)"/>
<xsl:otherwise>
<xsl:message> creating file: <xsl:value-of
select="$zoomhtml"/>
</xsl:message>
<xsl:result-document href="$zoomhtml">
</xsl:result-document>
</xsl:otherwise>
</xsl:choose>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
Duane Gran
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