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This paper aims to propose solutions to the issue of ontology visualization, by presenting intuitive and userfriendly ontology editing and visualization environments mainly oriented to domain experts. It starts with an overview of existing ontology visualization methods; afterwards it describes the Semantic DB system and the OWLeasyViz ontology editor. Semantic DB is a web application framework to create simple complete semantic web applications, integrating an ontology editor, a resource editor, an inference rule editor, a reasoner, and a search engine. OWLeasyViz is an ontology editor that combines a textual and a graphical representation of OWL ontologies. It meets different user needs by providing a simple and intuitive interface to end-users who are not ontologists, and offering more advanced tools to ontology experts. The OWLeasyViz editor is intended to be a module of a semantic web integrated working environment, developed within the context of a Swiss Government funded CTI applied research project in the domain of waste water management.

This paper presents a model for an electronic book (hyper‐book). Hyper‐books are electronic books defined on the basis of the paper book metaphor. This metaphor guarantees ease of use and understanding, as the paper counterpart is a well known concept. The hyper‐book maintains many of the features of paper books, in terms of interface design and available tools (orientation, navigation, personalisation) and provides added‐value that exploits the technology underlying it, such as searching, links and history mechanisms. We give a formal definition of the hyper‐book model as a dynamic system. The hyper‐book model is defined in terms of structural and functional components. Further, how the system evolves under the effects of these functional components is presented. The structural components reflect the book subdivision in pages, and the page subdivision in elements such as text, figure etc. The functional aspect is indispensable for describing the use of a dynamic and interactive system. In particular, a number of operators, which represent reader services, allow the user to change the system ‘state’. This simple model is intuitive, general and easy to extend. The hyper‐book model has been implemented in a working system, and evaluated with a group of users. The evaluation has confirmed that the adoption of the book metaphor is very effective, as it guarantees ease of using and understanding the system. The use of the hyper‐book model for organising and presenting electronic documents could have a considerable impact in the context of electronic publishing. A system, based on this model, could have a large applicability and diffusion in several fields such as electronic libraries, thanks to its user‐friendly interface.

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The aim of this paper is to provide an overview of current developments in the area of electronic books and libraries, and to describe an on‐going research project. Following a discussion of the key terminology used in this field, a number of issues will be investigated: what an electronic library is; how this concept has evolved during the last twenty years; what an electronic book is; and the relationship between an electronic library and an electronic book. As a result of our research we have defined a new concept, the Virtual Electronic Library, and its basic components: the hyper‐book and the visual‐book. These are two forms of electronic books which are built from different sources: paper books and electronic texts respectively. The environments in which such electronic books are produced will also be described.