What Data Types Does XSLT Sort Support?

The data-type attribute in the XSLT <xsl:sort> element controls how items are compared during node ordering, distinguishing between alphabetic collation and numerical evaluation. The standard W3C XSLT 1.0 and 2.0/3.0 specifications natively define two core enumerated values—text and number—while also allowing QName extension types or explicit XML Schema data types depending on the processor version.

Standard Data Types in XSLT 1.0

In XSLT 1.0, the data-type attribute accepts two primary standard values:

• text (Default): Instructs the XSLT processor to perform lexicographical (alphabetic) sorting based on Unicode code points or local collation rules. Under text sorting, the string "10" precedes "2" because the character '1' comes before '2'.
• number: Instructs the processor to evaluate the sort keys as floating-point numbers. Non-numeric values or empty nodes are evaluated as NaN (Not-a-Number), which typically sort before all valid numerical values in standard implementations.

XSLT 1.0 also allows a prefixed QName (Qualified Name) to support implementation-defined, vendor-specific sorting algorithms, though portable stylesheets generally stick to text and number.

Enhancements in XSLT 2.0 and 3.0

XSLT 2.0 and XSLT 3.0 expand on sorting capabilities through integration with W3C XML Schema data types:

• Standard Built-in Types: In addition to text and number, processors supporting Schema-Aware XSLT allow data-type to reference built-in XML Schema types such as xs:date, xs:dateTime, xs:time, xs:integer, xs:decimal, and xs:duration.
• Collation URI Integration: Rather than relying solely on data-type extensions for advanced text manipulation, modern XSLT specifications recommend using the collation attribute alongside data-type="text" to define language-sensitive, case-order, and natural sorting rules.

Basic Syntax Example

Sorting nodes numerically in an XSLT template:

<xsl:for-each select="product">
  <xsl:sort select="price" data-type="number" order="ascending" />
  <p><xsl:value-of select="name"/>: $<xsl:value-of select="price"/></p>
</xsl:for-each>