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# Monday, August 14, 2006

I've been given a task to fix several xsls (in fact many big xsls) that worked with msxml and stoped to work with .NET. At first I thought it will be easy stuff, indeed both implementations are compatible as both implement http://www.w3.org/1999/XSL/Transform.

Well, I was wrong. After a 10 minutes I've been abusing that ignorant who has written xsls. More over, I was wondering how msxml could accept that shit.

So, come to the point. I had following xsl:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform
   version="1.0"
   xmlns:msxsl="urn:schemas-microsoft-com:xslt"
   xmlns:user="http://mycompany.com/mynamespace">

<xsl:template match="/">
<HTML dir="rtl">
...
<BODY dir="rtl">
...
 <TD width="68" dir="ltr" align="middle">
 <FONT size="1" face="David">
  <xsl:variable name="DegB" select="//*[@ZihuyMuzar='27171']" />
  </FONT>
  </TD>
...
 <TD height="19" dir="ltr" align="middle">
 <FONT size="2" face="David">
  <xsl:value-of select="$DegB/*/Degem[1]/@*[3]" />
  %
  </FONT>
  </TD>
...

I don't want to talk about "virtues" of "html" that's produced by this alleged "xsl", however about xsl itself. To my amazement msxml sees $DegB, which is declared and dies in different scope. At first I thought I was wrong: "Must be scope is defined defferently then I thought?", but no. OK, I said to myself I can fix that. I've created another xsl that elevates xsl:variable declarations to a scope where they are visible to xsl:value-of.

But that wasn't my main head ache. Some genius has decided to use third, forth, and so on attribute. What does this mean in the god's sake? How one could rely on this? I'll kill him if I'll find him! There was thousands of such @*[3]. Even if I'll see the original xml how can I be sure that msxml and .NET handle attribute collections in the same order?

There was no other way, but check this assumption. I've verified that both implementations store attributes in xml source order. This easied my pains.

To clarify implementation details I have digged in XmlDocument/XPathDocument implementations in .NET 1.1 and 2.0. I was curious how they store a set of attributes. It's interesting to know that they has decided to keep only ordered list of attributes in either implementation. This means that ordered attribute access is fast, and named access leads to list scan. In my opinion it's dubious solution. Probably the idea behind is that there is in average a few attributes to scan when one uses named access. In my case there were up to 100 attributes per element.

Conclusion?
1. Don't allow to ignorants to come near the xsl.
2. Don't design xmls that use many attributes when you're planning to use .NET xslt.

Monday, August 14, 2006 1:42:06 PM UTC  #    Comments [0] -

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