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We describe an approach for multiparadigmatic visual access to databases, which is proposed to achieve seamless integration of different interaction paradigms. The user is provided with an adaptive interface augmented by a user model, supporting different visual representations of both data and queries. The visual representations are characterized on the basis of the chosen visual formalisms, namely forms, diagrams, and icons. To access different databases, a unified data model, the Graph Model, is used as a common underlying formalism to which databases, expressed in the most popular data models, can be mapped. Graph Model databases are queried through the adaptive interface. The semantics of the query operations is formally defined in terms of graphical primitives. Such a formal approach permits us to define the concept of 'atomic query,' which is the minimal portion of a query that can be transferred from one interaction paradigm to another and processed by the system. Since certain interaction modalities and visual representations are more suitable for certain user classes, the system can suggest to the user the most appropriate interaction modality as well as the visual representation, according to the user model. Some results on user model construction are presented. Index Terms - Visual query system, multiparadigmatic interaction, user model, adaptive visual interface, graph-based data model, heterogeneous databases.

Several applications use algorithms for drawing k-layered networks and, in particular, 2-layered networks (i.e., bipartite graphs). Bipartite graphs are commonly drawn in the plane so that all vertices lie on two parallel vertical lines, and an important requirement in drawing such graphs is to minimize edge crossings. Such a problem is NP-complete even when the position of the vertices on one layer is held fixed. This paper presents a heuristic, called the assignment heuristic, for edge crossing minimization in bipartite graphs, which works by reducing the problem to an assignment problem. The main idea of the assignment heuristic is to position simultaneously all the vertices of one layer, so that the mutual interaction of the position of all the vertices can be taken into account. We also show that the idea underlying the assignment heuristic can be effectively applied in other cases requiring edge crossing minimization.

Author(s): Martha E. Pollack [1]; Susanne E. Hambrusch [2]; Carla Schlatter Ellis [3]; Barbara J. Grosz [4]; Jessica Hodgins [5]; Ruzena Bajcsy [6]; Carla E. Brodley [7]; Luigia Carlucci Aiello [...]