applytemplates

apply-templates is a built-in instruction in XSLT that directs a stylesheet processor to apply template rules to a set of nodes. It allows a stylesheet to delegate formatting decisions to templates that match the input nodes, supporting flexible and modular transformation logic. The most common form is an instruction such as <xsl:apply-templates select="XPath" />, which evaluates the XPath expression to obtain a node-set from the current context and then processes each node by finding the most specific template that matches it. If the select attribute is omitted, the processor processes the current node’s children.

Templates can be organized into modes, which group templates for selective use. The mode attribute specifies a mode name; the processor then uses templates declared with match patterns in that mode. If no suitable template is found for a node in the chosen mode, the processor falls back to the built-in templates, which define default processing behavior such as copying elements or recursively applying templates to children.

Parameters can be passed to invoked templates via xsl:with-param elements inside xsl:apply-templates. This allows information to be transmitted to the templates that handle the selected nodes. A corresponding template can declare the parameter with xsl:param and access its value during processing.

Common usage examples include applying templates to all children with <xsl:apply-templates/>, applying templates only to certain elements with <xsl:apply-templates select="chapter"/>, and using a named mode like <xsl:apply-templates select="chapter" mode="summary"/> together with matching templates for that mode.

In summary, apply-templates is the primary mechanism in XSLT for driving template-based output generation, enabling precise control over how input nodes are transformed and rendered.