The increase in popularity of the XML format for representing data brought multiple challenges to the data management community, in particular concerning efficient query evaluation. At the same time, XML technologies are highly connected to distribution and data exchange, leading to the need for new distributed data management techniques. We present some results of our work on issues related to XML query processing. We first introduce a new language for describing materialized views, called XML Access Modules or XAMs, and a complete approach for XQuery evaluation based on XAM-specified views. We then discuss optimization techniques for ActiveXML, a language for the integration of distributed XML streams. Finally, we discuss architectures for handling large volumes of XML data on distributed hash tables, in the KadoP and ViP2P platforms developed in the Gemo group.