This paper is about the development of systems whose end users are professional people working in a specific domain (e.g., medicine, geology, mechanical engineering); they are expert in that domain, but not necessarily expert in nor even conversant with computer science. In several work organizations, end users need to tailor their software systems to better adapt them to their requirements and even to create or modify software artifacts. These are end-user development activities and are the focus of this paper. A model of the interaction between users and systems, which also takes into account their reciprocal coevolution during system usage, is discussed. This model is used to define a methodology aimed at designing software environments that allow end users to become designers of their own tools. The methodology is illustrated by discussing two experimental cases.

Computers are increasingly being seen not only as computing tools but more so as communication tools, thus placing special emphasis on human-computer interaction (HCI). In this article, the focus is on visual HCI, where the messages exchanged between human and computer are images appearing on the computer screen, as usual in current popular user interfaces. We formalize interactive sessions of a human-computer dialogue as a structured set of legal visual sentences, i.e., as a visual language, and show how rewriting systems can be generalized to specify both the pictorial and the computational aspects of visual languages. To this end, Visual Conditional Attributed Rewriting (VCARW) systems are introduced, and used for specification of visual languages. These specifications are given as inputs to a procedure illustrated in the article as a system of algorithms, which automatically generates control mechanisms of the interaction, thus favoring the design of more reliable and usable systems.

In the Information Society, end-users keep increasing very fast in number, as well as in their demand with respect to the activities they would like to perform with computer environments, without being obliged to become computer specialists. There is a great request to provide end-users with powerful and flexible environments, tailorable to the culture, skills, and needs of a very diverse end-user population. In this chapter, we discuss a framework for End-User Development and present our methodology for designing software environments that support the activities of a particular class of end-users, called domain-expert users, with the objective of making their work with the computer easier. Such environments are called Software Shaping Workshops, in analogy to artisan workshops: they provide users only with the necessary tools that allow them to accomplish their specific activities by properly shaping software artifacts without being lost in virtual space.

software Shaping Workshops (SSWs) described in this paper are s o f i a r e environments designed to support various activities of End-User Development (EUD) and tailoring. A design methodolog). to create easy-todevelop-and-tailor Visual Interactive Svstems that are organised asSSWs is illustrated. Users of an interactive system are in many cases experts in some domain different from Computer Science, who need to perform some task with the aid ofthe computer system. The design methodalagv allows users to directly collaborate to the system design and tailoring process to face co-evolution of users and systems. The srrategv feasibility is discussed, outlining its implementation through a web-based prototype.

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