In semantically rich hypertexts it is attractive to enable presentation of a network of nodes and links at different levels of abstraction. It is also important that the user can interact with the hypertext using a command repertoire that reflects the chosen abstraction level. Based on a characterization of rich hypertext we introduce the concept of an interaction engine that governs the separation between internal hypertext representation and external screen presentation. This separation is the key principle of the HyperPro system. The HyperPro interaction engine is based on simple rules for presentation, interpretation of events, and menu set up. Much of the power of the interaction engine framework comes from the organization of these rules relative to the type hierarchy of nodes and links, and relative to a hierarchy of so-called interaction schemes. The primary application domain discussed in the paper is program development and program documentation. Keywords: tailorability, int...

this paper we show how a text editor can be extended to include active text elements and give examples for how to apply these facilities to source code. Our approach is different from that of syntax-oriented editors in that our structuring is not based on the syntax of the edited texts. The implementation was done in the Oberon system which offers powerful mechanisms for extending software in an objectoriented way. KEY WORDS Active Text Hypertext Documentation Program editor Event trace diagrams MOTIVATION For centuries text was exclusively stored on paper. It was passive information that could be read or written, but nothing else. With the advent of electronic text processors operations such as inserting, deleting, and searching were introduced. But still text was passive in nature. Now that high-speed computers, graphical user interfaces, and multimedia become common, one starts to break with the passive paper metaphor and begins to consider text as an active medium.