With a focus on XML and web services, he has authored an maintains a number of the XML extensions within PHP as well as a contributor to libxml2 and libxslt within the Gnome project. Rob also occasionally writes articles for various publications on the use of XML and web services and also authored the book Pro PHP XML and Web Services. In his spare time, Rob also likes to work on identity related technologies, such as the openinfocard project and information card libraries.