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Visual query systems (VQSs) are query systems for databases that use visual representations to depict the domain of interest and express related requests. VQSs can be seen as an evolution of query languages adopted into database management systems; they are designed to improve the effectiveness of the human-computer communication. Thus, their most important(More)
Managing interschema knowledge is an essential task when dealing with cooperative information systems. We propose a logical approach to the problem of both expressing interschema knowledge, and reasoning about it. In particular, we set up a structured representation language for expressing semantic interdependencies between classes belonging to different(More)
In complex emergency scenarios, teams from various emergency-response organizations must collaborate. These teams include both first responders, such as police and fire departments, and those operators who coordinate the effort from operational centers. The Workpad architecture consists of a front- and a back-end layer. The front-end layer is composed of(More)
Information and communication infrastructures underwent a rapid and extreme decentralization process over the past decade: From a world of statically and partially connected central servers rose an intricate web of millions of information sources loosely connecting one to another. Today, we expect to witness the extension of this revolution with the wide(More)
Many recent proposals in the literature present easy-to-use query languages, based on visual representations of the database and direct manipulation mechanisms. Such proposals essentially deals with conventional query operations, whereas little effort is devoted to investigate friendly environments for querying temporal databases. Nevertheless, temporal(More)
During the past few years our research efforts have been inspired by two different needs. On one hand, the number of non-expert users accessing databases is growing apace. On the other, information systems will no longer be characterized by a single centralized architecture, but rather by several heterogeneous component systems. In order to address such(More)