David Carlisle

Monday, 19 November 2007

Opera joins the party

http://my.opera.com/desktopteam/blog/2007/11/16/even-more-work

In this build, we added MathML support out of the box

Wednesday, 7 November 2007

After a wait of many years the STIX fonts have finally been released as public beta! These offer the promise of much better, more portable support for scientific documents on the web and elsewhere. The STIX fonts provide a uniform set of fonts that provide the glyphs for almost all the mathematical characters that have been added to unicode in recent years.

Initial testing suggests there may still be some problems with plane 1 characters (I just submitted the following comment to the stix beta test comment form...

I tested browser support (windows XP: Firefox, IE 7, Opera) with similar results in all three browsers. The quadruple integral displayed in all three browsers. The plane 1 alphabetic character did not display at all, FF displays 2 missing glyph boxes, IE shows 1 missing glyph box, and opera just shows white space..
I am not able to tell at this stage whether this is user error (I have not specified a sufficiently large set of the STIX fonts in CSS ?) or if this is due to lack of plane 1 support in the browsers, or if there is a problem with the unicode tables in the stix fonts, so I supply the small test file below, which I expect to render as as
QUADRUPLE INTEGRAL OPERATOR
MATHEMATICAL BOLD CAPITAL A
<html>
<head>
<title>stix</title>
<style>
p {
font-family: STIXGeneral, STIXGeneral-Italic, STIXGeneral-Bold, STIXGeneral-BoldItalic;
}
</style>
</head>
<body>
<p>x2a0c &#x2a0c;</p>
<p>x1d400 &#x1d400;</p>
</body>
</html>

Friday, 5 October 2007

New MathML Draft

The W3C just published the latest draft of MathML 3. As ever, comments welcome on www-math@w3.org mailing list.

Tuesday, 12 June 2007

XML position at NAG

NAG is looking for someone to work in the XML Technologies Group, that is, "my" group. So if you are interested, please contact the address specified in the above posting.

Tuesday, 5 June 2007

The Big Switch

There was a thread a while ago on xsl-list discussing when was a good time to switch from XSLT1 to XSLT2. The consensus seemed to be, "it depends...."

For NAG, the answer is NOW!

After a lot of regression testing, staring at diff files and crossing of fingers, we just switched the processor for our main stylesheets over from saxon 6 to saxon 8.

This is quite a large (set of) stylesheets (around 26K lines of XSLT) so is quite a substantial test of XSLT2's compatibility with XSLT1. The results were pretty good, although it's not exactly surprising as an earlier version of these stylesheets were used to request improvements to backward compatibility mode as defined in an earlier draft, all the main changes requested in that report were made.

We are taking a multi-stage process to switching to version 2:

Import an XSLT2 stylesheet that defines a few extension functions in the saxon 6 extension namespace using xsl:function and standard function calls. saxon:node-set defined as identity function, saxon:tokenize defined using XPath2 tokenize, saxon:distinct defined using XPath2 distinct-values etc.
Process the stylesheets with saxon 8 over the NAG Library documentation for Fortran and C and check the results were the same.
The only significant difference was due not so much to a change of language but to the change of processor. Saxon has changed its default ordering for xsl:sort. As documented, adding lang="en" reverted the behaviour.
Start using XSLT2 features in the stylesheet, and start removing the existing calls to saxon6 extension functions. (This is where we are now.) This will eventually remove the need for the functions defined in step 1.
(Some time soon.) Change the specified version on the stylesheets from 1.0 to 2.0. This will turn off BC mode and will require another round of regression testing. As noted in the old email above, the stylesheets often pass parameters to named templates that do not define those parameters, which will become an error. this will be easy to find as the error is fatal and so you just fix them. Harder will be finding all the places where XSLT1's implicit "first node in document order" semantics have been used. Fortunately in our case we have a large, but relatively stable document collection to process, so it's feasible to make this change and then run automated comparisons over the results of processing the entire collection in the two modes.

This is far from being the first use of XSLT2 at NAG, but it's the first time we've switched a stylesheet collection from version 1 to version 2, so far things have gone pretty smoothly...

Tuesday, 29 May 2007

The EXSLT node-set function

Following on from a thread on xsl-list which turned to the question of support for the useful xx:node-set() extension function in the XSLT engines used by popular browsers.

Using XPath extension functions in a cross-browser environment is greatly simplified if all the XSLT engines use the same extension namespace. This was one of the motivating reasons behind the community initiative to standardise on the EXSLT extension namespaces.

Opera's XSLT engine supports exslt:node-set, Mozilla/Firefox's XSLT engine doesn't in the current release, but does in the "Gran Paradiso" alpha tests for Firefox 3. Internet Explorer (6 and 7) don't support EXSLT, but do support the functionally identical msxsl:node-set function in the usual msxsl extension namespace.

The usual way to handle exslt:node-set and msxsl:node-set in the same document is to use xsl:choose blocks, with tests on function-available('exslt:node-set') but that is often inconvenient if you want to use xx:node-set in the middle of an XPath.

In the above XSL-List thread I casually suggested that an alternative would be to just always use exslt:node-set in the body of the stylesheet and use the msxsl:script extension to define exslt:node-set for IE. That turned out not to be as easy as I thought as node-set isn't a valid function name in either of the supported extension languages in msxsl (JScript or VBScript). However Julian Reschke came up with the construct needed, use associative array syntax so you can use ['node-set'] to define the function. A complete stylesheet using this technique is shown below

<xsl:stylesheet
  version="1.0" 
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:exslt="http://exslt.org/common"
  xmlns:msxsl="urn:schemas-microsoft-com:xslt"
  exclude-result-prefixes="exslt msxsl">
  

<msxsl:script language="JScript" implements-prefix="exslt">
 this['node-set'] =  function (x) {
  return x;
  }
</msxsl:script>


<xsl:variable name="x">
  <y/>
</xsl:variable>

<xsl:template match="x">
  <html>
    <head><title>test exslt node set</title></head>
    <body>
      <xsl:apply-templates select="exslt:node-set($x)/*"/>
    </body>
  </html>
</xsl:template>

<xsl:template match="y">
  <p>node set!</p>
</xsl:template>

</xsl:stylesheet>

The same stylesheet is online together with a test file which just consists of a stylesheet reference and an empty element <x/>.

If your browser supports EXSLT (either natively or using the technique above) viewing the test file link should show "node set!". This appears to work in Firefox Gran paradiso, Internet Explorer 7, Opera 9.21. It doesn't work in Firefox 2 (you get an error message about an unsupported extension function). Users of other browsers that support XSLT (Safari?) feel free to report any results in the comments!

Updated 2008-08-06 to move test file to a different server.

Updated 2009-12-17 to move to google code server. The file now reports that Safari 3.2 supports node-set

Wednesday, 9 May 2007

schematron updates

Ken Holman posted a problem with the skeleton which also applied to my version described in an earlier post so I updated the code, at the same URI. There have also been some updates in the last few days removing saxon dependencies, as described in the coments, thanks to Colin Adams for picking those up. [updated again 2007/05/09] A couple of errors had crept into the schematron-get-full-path mode used to display the XPath of the current node.