Maria Luisa Sapino

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Although several access control policies can be devised for controlling access to information, all existing authorization models, and the corresponding enforcement mechanisms, are based on a specific policy (usually the closed policy). As a consequence, although different policy choices are possible in theory, in practice only a specific policy can actually(More)
The need to automatically extract and classify the contents of multimedia data archives such as images, video, and text documents has led to significant work on similarity based retrieval of data. To date, most work in this area has focused on the creation of index structures for similarity based retrieval. There is very little work on developing formalisms(More)
Over the last few years, there has been a tremendous increase in the number of interactive multimedia presentations prepared by different individuals and organizations. In this paper, we present an algebra for creating and querying interactive multimedia presentation databases. This algebra operates on trees whose branches reflect different possible(More)
The problem of integrating multiple heterogeneous legacy databases is an important problem. Many papers 7, 9, 3] to date on this topic have assumed that all the databases comprising a mediated/federated system share the same security ordering. This assumption is often not true as the databases may have been developed independently by diierent agencies at(More)
The problem of view updating in databases consists in modifying the extension of view relations (i.e., relations defined in terms of “base” ones) transforming only the content of the extensional database, i.e., the extensional representation of base relations. This task is non-deductive in nature and its relationships with non-monotonic reasoning, and(More)
Feedback process has been used extensively in document-centric applications, such as text retrieval and multimedia retrieval. Recently, there have been efforts to apply feedback to semi-structured XML document collections as well. In this paper, we note that feedback can also be an effective tool for exploring (through result ranking and query refinement)(More)
In many applications, the underlying data (the web, an XML document, or a relational database) can be seen as a graph. These graphs may be enriched with weights, associated with the nodes and edges of the graph, denoting application specific desirability/penalty assessments, such as popularity, trust, or cost. A particular challenge when considering such(More)
Over the last few years, there has been a tremendous increase in the number of interactive multimedia presentations prepared by different individuals and organizations. In this paper, we present an algebra for querying multimedia presentation databases. In contrast to the relational algebra, an algebra for interactive multimedia presentations must operate(More)