Most conventional design processes produce documentation as a by-product: design is done within an environment or collection of tools and the design outputs, models, diagrams, results, etc are gathered together along with commentary (usually with hindsight) into some kind of document at the end of the process. Inspired by ideas taken from literate programming and notebook interfaces to design tools, a prototype document centred design document has been developed. In such an environment, the document is the main product and the design is a by-product of documenting the design. By implementing the framework components of the system in Java and by using the extended markup language (XML) to encode the contents of the documents, the system is made platform neutral and therefore portable. An example document centred environment for computer-aided control system design (CACSD), that integrates MATLAB and SIMULINK with the document-based framework, is briefly described and indications for future possibilities for this technology are given.