From its origins in document processing, XML has developed into a medium for communicating all kinds of data between applications. More recently, interest has focused on the concept of native XML databases. This paradigm requires that database queries can be resolved by direct searching of XML data structures. Relational databases can be compressed without the loss of direct addressability. A similar approach can be applied to XML data structures. Compression in the relational paradigm is associated with improved performance. We review this approach and show results from the implementation of a prototype compressed DOM. Our research indicates that it is possible to optimise queries over compact XML structures by choosing appropriate physical representations.