Re: Schematron tip: Use only one pattern

“Why is validation so slow?” I wondered.

I did some digging and discovered the reason for the slowness. Recall that a Schematron schema is converted to an XSLT program. I looked at the XSLT program that was generated for my Schematron schema. Here’s what I found:

   <xsl:template match="/">
      <xsl:apply-templates select="/" mode="M0"/>
      <xsl:apply-templates select="/" mode="M1"/>
      <xsl:apply-templates select="/" mode="M2"/>
      <xsl:apply-templates select="/" mode="M3"/>

      …
      <xsl:apply-templates select="/" mode="M29"/>
   </xsl:template>

 

That says: Start at the top of the XML document and process the entire XML document, applying the template rules with mode M0. Then, start all over at the top of the XML document and process the entire XML document, applying the template rules with mode M1. And so forth. 

 

So, the entire 180 MB XML file gets processed 30 times.

 

Eek!

 

It’s no wonder that validation was so slow.