This work is related to hypermedia authoring and execution environments, and its main focus is declarative document authoring. Aiming at improving the expressiveness and reuse in the specification of hypermedia documents, this work introduces the hypermedia authoring languages X-SMIL and NCL - Nested Context Language - version 2.1. Exploiting the concept of templates, X-SMIL allows the definition of new semantics for SMIL compositions, besides its usual seq, par and excl elements. X-SMIL templates are specified using an XTemplate profile, which extends the original idea of the NCL XTemplate language. Bringing new facilities for template definitions, this new profile is used to further improve the NCL language. X-SMIL also offers support for handling hypermedia relations as first-class entities, through the use of hypermedia connectors - brought to X-SMIL via the NCL XConnector module. Another important goal of this work is to present a framework to facilitate the development of XML documents parsing and processing tools. Based on this framework, several compilers were implemented, permitting, among other features, the conversion of NCL documents into SMIL or X-SMIL specifications and vice- versa.