An XSL transformation is an XML document of declarations about how to rearrange the elements and attribute of another, source XML document. An XSL transformation might be seen as a "type" that derives from XML in the same way that any class definition ultimately extends the Object type.

An XSL transformation is made up of templates. Remember they are called "templates"; they are not functions. Templates always have a contextual relationship with the source document.

XSLT variables can only be assigned a value once. By chaining together declarations of variables/parameters based on values of other variables you can simulate mutability. It follows that incrementing a variable in the XSL equivalent of the for-next loop is obtained through a template 'chained' to itself (recursion). For more details about this, please see "Tip: Loop with recursion in XSLT" at:

http://www-128.ibm.com/developerworks/xml/library/x-tiploop.html?ca=dnt-626

XSLT variables/parameters are assigned values through their "select" attribute. What may not be readily apparent is that the xsl:variable and xsl:param elements can contain templates and/or xsl:template content. This implies that the procedural programming design pattern of assigning a function to a variable can be achieved in XSLT like this:

<xsl:variable name="has_supported_property">
    <xsl:choose>
        <xsl:when test="w:rPr/w:b">true</xsl:when>
        <xsl:when test="w:rPr/w:caps">true</xsl:when>
        <xsl:when test="w:rPr/w:i">true</xsl:when>
        <xsl:when test="w:rPr/w:dstrike">true</xsl:when>
        <xsl:when test="w:rPr/w:smallCaps">true</xsl:when>
        <xsl:when test="w:rPr/w:strike">true</xsl:when>
        <xsl:when test="w:rPr/w:u">true</xsl:when>
        <xsl:otherwise>false</xsl:otherwise>
    </xsl:choose>
</xsl:variable>

In procedural terms, the xsl:choose element above is part of an "anonymous template" that returns a value to the variable @has_supported_property. Note that contents of the xsl:when and xsl:otherwise elements are "result tree fragments." The example above should include xsl:text elements to really show this. This means that XSLT variables can be assigned fragments of XML.