The stm accessor is used to perform Simple Tree Manipulation operations on the operand document. STM is a language that performs XML operations at XPath locations in a processed document.

STM concentrates on tree manipulation operations only. Unlike XSLT, whose operations are defined in the transform domain, STM operations are defined in the document domain. This frequently has advantages.

STM operations are iterative with respect to the xpath target in the operand. That is if the xpath reference is multivalued the STM operation will be applied to all targets.

STM operations can incorporate substitutions from an optional param document. A <stm:param xpath="xxxx"> child element of an stm instruction is replaced by the fragment of the param document referenced by the xpath attribute of the param element.

The combination of STM and XSLT is very useful. For example STM template filling for XSLT generated templates is a common pattern, where XSLT is used to transform a document into a template and STM used to dynamically substitute documents into the template - this document was created using this pattern.

STM operations

stm:copy	Used to copy a document fragment into the operand document
stm:replace	Used to replace a document fragment in the operand document with child fragment
stm:get-fragment	Used to obtain a document fragment from the operand document
stm:create-path	Generate and attach a document fragment from an xpath expression at a given location
stm:append	Used to append a document fragment to the operand document at a given location
stm:insert-before	Used to insert a document fragment to the operand document before a given location
stm:insert-after	Used to insert a document fragment to the operand document before a given location
stm:set	Used to set a text element or attribute at a given location to a given value
stm:delete	Used to delete a text element or attribute at a given location
stm:regex	Used to return a regex results document of all fragments matching a regex expression
stm:apply-ns	Apply a namespace to the subtree below a given location
stm:remove-ns	Remove a namespace from the subtree below a given location
stm:replace-for-text	A matched element is replaced by a text node.
stm:rename	Rename an element or attribute retaining all children
stm:append-text	Append text to an element or attributes text value

A detailed tutorial of the STM language is available here