A multiparadigmatic visual environment for adaptive access to databases

Visual Query Languages (VQLs) are query languages essentially based on the use of visual representations to depict the domain of interest and express the related requests. Systems implementing a visual query language are called Visual Query Systems (VQSs) (a survey is in [1]). In recent years, many VQSs have been proposed in the literature adopting a range of different visual representations and interaction strategies. However, existing VQSs generally restrict the human-computer communication to only one kind of interaction paradigm. On the contrary, the presence of several paradigms, each one with different characteristics and advantages, will help both naive and experienced users to interact with the system. For instance, icons may well evoke the objects present in the database, while relationships among them may be better expressed through the edges of a graph, and collections of instances may be easily arranged into a form. The way in which the query is expressed also depends on the chosen visual representation. In the existing VQSs, queries on diagrammatic representations are mainly expressed by following links, forms are often filled with prototypical values, and iconic queries can be constructed by spatially composing primitive icons. In the system we propose, the same interface can offer to the user different interaction mechanisms for expressing a query, depending on both the experience of the user and the kind of the query itself. The selection of the appropriate interaction paradigm can be made with reference to a user model that describes the user interests and skills [5, 3]. Such a model should be dynamically maintained according to the history of the interactions, i.e., both queries and user reactions to system messages. In our approach we offer to the user a multiparadigmatic visual interface for expressing the query, with the possibility of switching between different visual representations to exploit their unique features, and the support for accessing databases expressed in different models. Presently, existing VQSs are limited to interface databases expressed in a single model by using a specific representation. In our approach we propose to use a common underlying model, namely the Graph Model (GM) [2], which is powerful enough to represent the databases expressed in the most common data models. Graph Model Data Bases (GMDBs) can be queried by means of the above multiparadigmatic interface. The semantics of the query