From: W. Trevor King <wking@drexel.edu>
Date: Fri, 1 Jul 2011 14:32:10 +0000 (-0400)
Subject: Add Gramps-sorting example to XSLT post.
X-Git-Url: http://git.tremily.us/?a=commitdiff_plain;h=9b7d849a728e38a17f23b9b2d107fbe0266b444d;p=blog.git

Add Gramps-sorting example to XSLT post.
---

diff --git a/posts/XSLT.mdwn b/posts/XSLT.mdwn
index 512c744..03b4731 100644
--- a/posts/XSLT.mdwn
+++ b/posts/XSLT.mdwn
@@ -12,10 +12,54 @@ simple [[example|chapter]] from this intro and also included a
 [[slightly more complicated setup|code]] for generating online help
 for a list of macros.
 
+XSLT is also useful for standardizing XML content.  For example, I was
+recently trying to compare to [[Gramps]] XML files, to see what had
+changed between two database backups.  Unfortunately, the backup XML
+was not sorted by `id`, so there were many diff chunks due to node
+shuffling that didn't represent any useful information.  With the
+following XSLT:
+
+    <?xml version="1.0"?>
+    <xsl:stylesheet version="1.0"
+                    xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+    	<xsl:output method="xml" indent="yes"/>
+    	<xsl:strip-space elements="*"/>
+    	<!-- identity transform -->
+    	<xsl:template match="@*|node()">
+    		<xsl:copy>
+    			<xsl:apply-templates select="@*|node()"/>
+    		</xsl:copy>
+    	</xsl:template>
+    	<!-- sort node children by their `id` attributes -->
+    	<xsl:template match="node()">
+    		<xsl:copy>
+    			<xsl:apply-templates select="@*"/>
+    			<xsl:for-each select="node()">
+    				<xsl:sort select="@id" order="ascending"/>
+    				<xsl:apply-templates select="."/>
+    			</xsl:for-each>
+    		</xsl:copy>
+    	</xsl:template>
+    </xsl:stylesheet>
+
+With the above saved as `sort-by-id.xsl`, you can sort `some.xml` using
+
+    $ xsltproc --nonet --novalid sort-by-id.xsl some.xml
+
+You can compare two [[Gramps]] XML files with
+
+    $ diff -u <(zcat wtk_2011-06-30b.gramps | xsltproc --nonet --novalid sort-by-id.xsl -)
+              <(zcat wtk_2011-06-30d.gramps | xsltproc --nonet --novalid sort-by-id.xsl -) | less
+
+Jesper Tverskov has a nice page about [the identity template and
+related tricks][identity] if you want more examples of quasi-copy
+transforms.
+
 [XSLT]: http://www.w3.org/TR/xslt
 [w3]: http://www.w3schools.com/xsl/
 [intro]: http://nwalsh.com/docs/tutorials/xsl/xsl/slides.html
 [xsltproc]: http://www.xmlsoft.org/XSLT/
+[identity]: http://www.xmlplease.com/xsltidentity
 
 [[!tag tags/tools]]
 [[!tag tags/web]]