The XML Backplane: Pluggable Elements of the XML Interactive Architecture XML defines an extensible syntax mechanism that allows you to combine markup from different XML applications; but if those applications are not semantically compatible, it becomes very hard to effectively combine them. The XML Backplane is an effort ongoing at W3C to identify common architectural features of several existing XML applications, such as SMIL, XForms, Voice XML and XHTML, and define these features independently and consistently to allow them to be adopted in these and other applications, ensuring consistency across applications, and making user agents that combine different applications easier to write. An example feature is submission, where data must be selected, serialised in one of several ways, sent to the server, and the reply dealt with in one of several different manners; but others include the handling of events in general, the definition of abstract or device-independent events, document navigation, and data storage. The collection of these features creates a common infrastructure for both imperative and declarative application architectures,helping to align and integrate these approaches as necessary. This talk gives an overview of the backplane and the efforts ongoing to define it. -- The Backplane is a W3C effort to identify common architectural features of XML applications, and define them independently and consistently ensuring consistency across applications.