<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
>
<xsl:output method="text"/>
<xsl:template match="xsd:simpleType">
sub <xsl:value-of select="@name" /> {
    <xsl:for-each select="xsd:annotation/xsd:documentation"># <xsl:val
+ue-of select="normalize-space(.)" /></xsl:for-each>
    my($class, $value) = @_;
    return FALSE if _is_null($value);
    return <xsl:for-each select="xsd:restriction"><xsl:value-of select
+="replace(@base,':', '_')" />($value) and <xsl:apply-templates mode="
+restriction" select="*"/>TRUE;</xsl:for-each>
}
</xsl:template>
<xsl:template mode="restriction" match="xsd:minInclusive">$value &gt;=
+ <xsl:value-of select="@value" /> and </xsl:template>
<xsl:template mode="restriction" match="xsd:minExclusive">$value &gt; 
+<xsl:value-of select="@value" /> and </xsl:template>
<xsl:template mode="restriction" match="xsd:maxInclusive">$value &lt;=
+ <xsl:value-of select="@value" /> and </xsl:template>
<xsl:template mode="restriction" match="xsd:maxExclusive">$value &lt; 
+<xsl:value-of select="@value" /> and </xsl:template>
</xsl:stylesheet>
[download]

  
sub longitudeType {
    # The longitude of the point. Decimal degrees, WGS84 datum.
    my($class, $value) = @_;
    return FALSE if _is_null($value);
    return xsd_decimal($value) and $value >= -180.0 and $value < 180.0
+ and TRUE;
}
[download]

It doesn't work in XML Notepad, because of the replace (which replaces the colon with an underscore). Without it, it works in MS XML Notepad, too — except for the missing substitution, of course.

For kicks, I've processed the original XSD file this way, and (apart from some junk from those element that are now not handled in the XSD file) I get this:

This is fun.

p.s. I used TRUE and FALSE as booleans for readability. You can always replace them with 1 and 0, but I would prefer constants.

Update brian asked how hard it is to extend to process other types too, in particular, fixType (enumeration). That turned out to be an addition of a few extra lines. I've also done a few extra modifications so it puts a package declaration at the top, a "1;" at the bottom, and suppression of the junk. The result is here:

It doesn't work in XML Notepad, because of the replace

MS has only poor support for EXSLT which also is the case for its string extensions of XPath 1.0 (replace).

Standard XPath 1.0 offers translate (somewhat like tr in Perl). For your purpose just do a s/replace/translate/ and even limited renderer like XML Notepad are satisfied. (tested)