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Data integration is the problem of combining data residing at distributed heterogeneous sources, including multimedia sources, and providing the user with a unified view of these data. Ontology based Data Integration involves the use of ontology(s) to effectively combine data and information from multiple heterogeneous sources. Ontologies, with respect to(More)
We propose the demonstration of Keymantic, a system for keyword-based searching in relational databases that does not require a-priori knowledge of instances held in a database. It finds numerous applications in situations where traditional keyword-based searching techniques are inappli-cable due to the unavailability of the database contents for the(More)
A new kind of metadata offers a synthesized view of an attribute's values for a user to exploit when creating or refining a search query in data-integration systems. The extraction technique that obtains these values is automatic and independent of an attribute domain but parameterized with various metrics for similarity measures. The authors describe a(More)
Data warehouse architectures rely on extraction, transformation and loading (ETL) processes for the creation of an updated, consistent and materialized view of a set of data sources. In this paper, we aim to support these processes by proposing a tool for the semi-automatic definition of inter-attribute semantic map-pings and transformation functions. The(More)
In this paper, we follow the role-based access control (RBAC) approach and extend it to provide for the dynamic association of roles with users. In our framework, privileges associated with resources are assigned depending on the attribute values of the resources, attribute values associated with users determine the association of users with privileges, and(More)
We investigate a security framework for collaborative applications that relies on the role-based access control (RBAC) model. In our framework, roles are pre-defined and organized in a hierarchy (partial order). However, we assume that users are not previously identified, therefore the actions that they can perform are dynamically determined based on their(More)
Research on data integration has provided a set of rich and well understood schema mediation languages and systems that provide a meta-data representation of the modeled real world, while, in general, they do not deal with data instances. Such meta-data are necessary for querying classes result of an integration process: the end user typically does not know(More)