Re: [xsl] character map "range" in XSLT

["G. Ken Holman" <gkholman@xxxxxxxxxxxxxxxxxxxx>]

At 2010-05-12 13:49 -0400, David wrote:
> I'm writing a XSLT that has to translate XML to plain ascii 
> text.  The XML contains unicode characters, possibly any of them.  I 
> cannot control the authoring so I must handle whatever is thrown at me.
>
> I have a few dozen specially know character translations for things 
> like 1/4 and degrees unicode symbols.
> But I have a need to "catch all" charactors that are not mapped 
> explicitly (rather then map explicitly the entiure unicode set) and 
> translate them into something like "<UNKNOWN CHARACTER>"
>
> Any suggestions on how to do this ? I could trivially write a 
> post-processor to do this (maybe a dozen lines of C or java) but if 
> there's a feature directly in XSLT I'd love to try that.
>
> Any ideas welcome !

You could try a general match on all text nodes and then using 
Unicode code points to accept only ASCII text between code points 32 
and 126 (or 127 depending on your need)(and I've included some 
diagnostic since that might help the reader):

 <xsl:template match="text()">
    <xsl:for-each select="string-to-codepoints(.)">
      <xsl:value-of select="if ( . ge 32 and . le 127 )
                            then codepoints-to-string(.)
                            else concat('&lt;UNKNOWN CHARACTER-',.,'>')"/>
    </xsl:for-each>
  </xsl:template>

It could be slow, but I think it will be faster than using substring().

Remember there is an ISO DSDL standard that is for validating exactly 
this:  the use of Unicode characters in an XML document.  It is 
called CREPDL for "Character Repertoire Description Language":

 http://www.iso.org/iso/catalogue_detail.htm?csnumber=51085
 http://www.asahi-net.or.jp/~eb2m-mrt/crepdl/ns/structure/1.0/index.xml
 http://www.assembla.com/spaces/CrepdlValidatorInFsharp

I understand you are implementing a transformation and 
character-level validation doesn't apply, but since you have such a 
requirement for using only a subset of characters, there may be a 
role for CREPDL in your information/validation flow in addition to 
what you are asking for in this post.

I hope this helps.

. . . . . . . . . . . Ken

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