XML transformation language

An XML transformation language is a programming language designed specifically to transform an input XML document into an output document which satisfies some specific goal.

The XML (EXtensible Markup Language) to Data transformation contains some important cases.

The earliest transformation languages predate the advent of XML as an SGML profile, and thus accept input in arbitrary SGML rather than specifically XML.

These include the SGML-to-SGML link process definition (LPD) format defined as part of the SGML standard itself; in SGML (but not XML), the LPD file can be referenced from the document itself by a LINKTYPE declaration, similarly to the DOCTYPE declaration used for a DTD.

[1] Other such transformation languages, addressing some of the deficiencies of LPDs, include Document Style Semantics and Specification Language (DSSSL) and OmniMark.