A category consists of an outer category element containing the following: name: the canonical name for the category path: The canonical path to the category consisting of the concatenated names of the parents from the root category separated by "/" lastmod: The UTC date time of last modification created: The UTC date time of creation deprecated: An empty element defining this as a deprecated category. namespace: An empty element defining this as a namespace. display-names: contains 0 or more display names. Each MUST have a different lang attribute descriptions: contains 0 or more description elements. Each MUST have a different lang attribute references: contains 0 or more reference elements each of which is the URI of a potentially useful related category. aliased-to: If present this is an alias for the referenced category. The value is a URI. categories: On retrieval may be populated with child categories. The root category conceptually has an empty name and is referenced by "/". The direct children of the root are namespace categories and define a namespace for all children of that category. The namespace category may contain an aliased-to element which effectively redirects to the target which may be an external category server.