#XSLT Instructions Reference

Every XSLT instruction is an XML element in the xsl: namespace that controls how the transformation proceeds. This reference covers all instructions supported by the PhoenixmlDb XSLT engine, organized by purpose.

#Instruction Categories

Category	Instructions	Description
Output	value-of, text, comment, processing-instruction, sequence, message	Producing text, nodes, and diagnostic output
Control Flow	if, choose/when/otherwise, switch, where-populated, on-empty, on-non-empty	Conditional processing
Variables and Parameters	variable, param, with-param	Declaring and passing values
Iteration and Sorting	for-each, sort, perform-sort, iterate, break, next-iteration	Looping and ordering
Grouping	for-each-group	Four grouping modes with current-group() and current-grouping-key()
Copying and Identity	copy, copy-of, mode on-no-match	Copying nodes and the identity transform pattern
Node Construction	element, attribute, namespace, document	Building nodes with dynamic names
Multiple Outputs	result-document, output	Generating multiple files and controlling serialization
Functions	function	Defining reusable functions callable from XPath
Keys and Cross-References	key	Indexing documents for fast lookup
String Analysis	analyze-string, matching-substring, non-matching-substring	Regex-based string processing
Error Handling	try, catch, assert, fallback	Handling errors and asserting conditions
Merging	merge, merge-source, merge-key, merge-action	Combining sorted input sources
Maps, Arrays, and Records	map, map-entry, array, array-member, for-each-member, record	Constructing structured data (XSLT 3.0/4.0)
Streaming and Accumulators	source-document, accumulator, accumulator-rule, fork	Processing large documents efficiently
Packages	use-package, accept, override, expose	Reusable stylesheet libraries with visibility control
Dynamic Evaluation	evaluate	Runtime XPath evaluation
Number Formatting	number, decimal-format, character-map	Numbering schemes and format customization

#Quick Reference

Every instruction follows this pattern:

<xsl:instruction-name attribute="value">
  <!-- content (other instructions or literal output) -->
</xsl:instruction-name>

Instructions can appear in two places:

Top-level declarations (children of xsl:stylesheet) — xsl:template, xsl:variable, xsl:function, xsl:key, xsl:output, etc.
Sequence constructors (inside templates and functions) — xsl:value-of, xsl:for-each, xsl:if, etc.

Some instructions (like xsl:variable and xsl:param) can appear in both positions with slightly different semantics.