The EDD defines the structure of a document where meaningful units are designated as elements nested in each other depending on their relationships, and where the formatting of these elements is based on their contexts. Attributes or Metadata can be added to these elements and used for single source publishing or for filtering elements during the output processes (such as publishing for print or for Web-based display). The author can view the conditions and contexts in a tree-like structure derived from the grammar (as specified by the DTD) or as formatted in a typical final output form.