MarkLogic Content Server, from MarkLogic, is a professional, highly scalable, XQuery-based XML repository.

Although based on XQuery, MarkLogic includes extensions to the query language that take advantage of its ability to update content (down to any level in the structure) and to index text for free-text searching. Other features include tag-level content lexicons, point-in-time queries, a built-in web-server, a document classified that takes note of the XML structure as well as the text content, etc etc etc.