The simplicity of Web-based data exchange is beneficial for nonformal, semiformal and formal documents. For formal specifications and programs the Web permits distributed development, usage and maintenance. Logic programming (LP) has the potential to serve as a uniform language for this. Meanwhile, however, the World Wide Web Consortium (W3C; http://www.w3.org/) has enhanced HTML–for nonformal and semiformal documents–into the Extensible Markup Language (XML) (Harold, 1999)–for semiformal and formal documents. This raises the issue of the relationships between XML and LP. Will logic programming have the chance, despite, or perhaps precisely because of XML, to become a ‘Web technology’ for formal documents? Could the HTML-like syntax of XML be replaced by a Prolog-like syntax, or could it be edited or presented over a standardized stylesheet—in such a Prolog syntax? Is SLD resolution a suitable starting point for the interpreter semantics of an XML query language like XQL (http://www.w3.org/TandS/QL/QL98/pp/xql.html) or should an LP-oriented, inferential query language be developed in the form of an XML-based Prolog? In the following text, such questions will be discussed, and possible interplays between XML and LP—in both directions—will be presented.