Integrating multimedia characteristics in web-based document languages

A single multimedia document model needs to include a wide range of different types of information. In particular, information about space and time is essential for determining the spatial and temporal placement of elements within a presentation. Each information type included in a document model requires its own structuring mechanisms. The language used to express the document model has to be able to encapsulate the plurality of required structures. While this is a process that can be carried out relatively easily during the initial design of a language, it is more difficult in the case that a particular document language already exists and extra multimedia characteristics are required. For example, one could consider adding temporal information to an existing 'static' document language. We investigate the underlying problems of superimposing a new document feature on an existing language and discuss possible strategies for integrating the required extra information in a modified document description language.