The extensible markup language (XML) has been applied successfully in a wide range of application domains and is beginning to find applications in visualisation. We explore the possibility that, rather than simply being used as an exchange format, XML might become a fundamental medium in an extended visualisation pipeline. We present examples from our software visualisation research to illustrate that increased rigour, as well as flexibility, can be delivered by integrating XML into the visualisation pipeline. Keywords-- Visualisation, XML, VRML