Providing an integrated access to multiple heterogeneous sources is a challenging issue in global information systems for cooperation and interoperability. In this context, two fundamental problems arise. • First, how to determine if the sources contain semantically related information, that is, information related to the same or similar real-world concept(s). Second, how to handle semantic heterogeneity to support integration and uniform query interfaces. Complicating factors with respect to conventional view integration techniques are related to the fact that the sources to be integrated already exist and that semantic heterogeneity occurs on the large-scale, involving terminology, structure, and context of the involved sources, with respect to geographical, organizational, and functional aspects related to information use. Moreover, to meet the requirements of global, Internet-based information systems, it is important that tools developed for supporting these activities are semi-automatic and scalable as much as possible. The goal of this paper is to describe the MOMIS [4, 5] (Mediator envirOnment for Multiple Information Sources) approach to the integration and query of multiple, heterogeneous information sources, containing structured and semistructured data. MOMIS has been conceived as a joint collaboration between University of Milano and Modena in the framework of the INTERDATA national research project, aiming at providing methods and tools for data management in Internet-based information systems. Like other integration projects [1, 10, 14], MOMIS follows a "semantic approach" to information integration based on the conceptual schema, or metadata, of the information sources, and on the following architectural elements: i) a common object-oriented data model, defined according to the ODLxs language, to describe source schemas for integration purposes. The data model and ODLxs have been defined in MOMIS as subset of the ODMG-93 ones, following the proposal for a standard mediator language developed by the I3/POB working group [7]. In addition, ODLxs introduces new constructors to support the semantic integration process [4, 5]; ii) one or more wrappers, to translate schema descriptions into the common ODLIs representation; iii) a mediator and a query-processing component, based on two p~e-existing tools, namely ARTEMIS [8] and ODB-Tools [3] (available on Internet at http://sparc20.dsi.unimo.it/), to provide an 13 architecture for integration and query optimization. In this paper, we focus on capturing and reasoning about semantic aspects of schema descriptions of heterogeneous information sources for supporting integration and query optimization. Both semistructured and structured data sources are taken into account [5]. A Common Thesaurus is constructed, which has the role of a shared ontology for the information sources. The Common Thesaurus is built by analyzing ODLI3 descriptions of the sources, by exploiting the Description Logics OLCD (Object Language with Complements allowing Descriptive cycles) [...

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This Java-based access-control system supports secure XML document administration at varying levels of granularity.

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The development of a security system is generally performed through a multiphase methodology, starting from the initial preliminary analisys of the application environment, up to the physical implementation of the security mechanisms. In this framework, we propose a new approach for the development of security systems based on the reuse of existing security specifications. In the paper we illustrate how reusable specifications can be built by analyzing existing security systems, and how they can be used to develop new security systems not from scratch.

Introducing the A-Posteriori Affinity Propagation (APP) algorithm for incremental clustering with cluster consolidation and stratification • Faithfulness and forgetfulness properties in evolutionary clustering for tracing cluster changes over time • Application of incremental clustering to Semantic Shift Detection and diachronic document corpus analysis • Comparison with benchmark algorithms, namely Affinity Propagation (AP) and Affinity Propagation based on NearestNeighbor Assignment (IAPNA), and discussion on scalability benefits

The rapid growth of the Web and the ease with which data can be accessed facilitate the distribution and sharing of information. Information dissemination often takes the form of documents that are made available at Web servers, or that are actively broadcasted by W eb servers to interested clients. In this paper, we present an XML-compliant formalism for specifying security-related information for Web document protection. In particular, we introduce X-Sec, an XML-based language for specifying subject credentials and security policies and for organizing them into subject pro les and policy bases, respectively. The language is complemented by a set of subscription-based schemes for accessing distributed Web documents, which rely on de ned XML subject pro les and XML policy bases.

Author-is a Java-based system for access control to XML documents. Author-implements a discretionary access control model specifically tailored to the characteristics of XML documents. In particular, our system allows (i) a set-oriented and single-oriented document protection, by supporting authorizations both at document type and document level; (ii) a differentiated protection of document/document type contents by supporting multi-granularity protection objects and positive/ negative authorizations; (iii) a controlled propagation of authorizations among protection objects, by enforcing multiple propagation options.