Namespaces are a central building block of XML technologies today, they provide the identification mechanism for many XML-related vocabularies. Despite their ubiquity, there is no established mechanism for describing namespaces, and in particular for describing the dependencies of namespaces. We propose a simple model for describing namespaces and their dependencies. Using these descriptions, it is possible to compile directories of namespaces providing searchable and browsable namespace descriptions. Categories and Subject Descriptors: H.3.2 [Information Storage and Retrieval]: Information Storage -- File Organization General Terms: Management, Languages