MDA - markup/xml/xquery/xquery

Comment:: expression language, no statements: no side-effects
Comment:: uses XML Schema data types, and XML nodes have a type as well
Comment:: borrows path expressions from XPath, can be seen as extension thereof
Comment:: query language with a few extra programming features
Comment:: can also create new XML documents
history: influenced by Lorel, YATL, Quilt, XML-QL
Comment:: semantically similar to SQL

References: