This book is based on the NATO Advanced Research Workshop on Structures of Com munication and Intelligent Help for Hypermedia Courseware, which was held at Espinho, Portugal, April 19-24, 1990. The texts included here should not be regarded as untouched proceedings of this meeting, but as the result of the reflections which took place there and which led the authors to revise their texts in that light. The Espinho ARW was itself to some extent the continuation of the ARW on Designing Hypermedia/Hypertext for Learning, held in Germany in 1989 (D. H. Jonassen, H. Mandl (eds.): Designing Hypermedia for Learning. NATO ASI Series F, Vol. 67. Springer 1990). At that meeting an essential conclusion becarne apparent: the importance and interest of hyper media products as potential pedagogical tools. It was then already predictable that the enormous evolution of hypermedia would lead to its association with multimedia technologies, namely for the production of courseware. Parallel to the improvement of the didactic potential and quality which results from this association, it nevertheless brought along a natural array of difficulties, some old, some new, in the con ception and use of hypermedia products. Today there is agreement that one of the most promising technological advances for education is represented by the use of text, sound and images based on nonlinear techniques of information handling and searching of hypermedia architectures. The problem of hypermedia is fundamentally one of communication; this leads to an attempt at defining a language for hypermedia.