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 ODL I 3 language, to describe source schemas for integration purposes. The data model and ODL I 3 have been defined in MOMIS as subset of the ODMG-93 ones, following the proposal for a standard mediator language developed by the I

ranted provided that the copies are not made or distributed for direct commercial advantage, the VLDB copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Very Large Data Base Endowment. To copy otherwise, or to republish, requires a fee and/or special permission from the Endowment. Proceedings of the 26th VLDB Conference, Cairo, Egypt, 2000. 2 MOMIS is a joint project among the Universit`a di Modena e Reggio Emilia, the Universit`a di Milano, and the Universit`a di Brescia within the national research project INTERDATA, theme n.3 "Integration of Information over the Web", coordinated by V. De Antonellis, Universit`a di Brescia. 1. a common data model, ODM I 3 , which is defined according to the ODL I 3 language, to describe source schemas for integration purposes. ODM I 3 and ODL I 3<F12.24

SI-Designer (Source Integrator Designer) is a designer support tool for semi;automatic integration of heterogeneous sources schemata (relational, object and semi;structured sources); it has been implemented within the MOMIS project and it carries out integration following a semantic approach which uses intelligent Description Logics-based techniques, clustering techniques and an extended ODMG-ODL language, ODL I 3, to represent schemata, extracted, integrated information. Starting from the sources ’ ODL I 3 descriptions (local schemata) SI-Designer supports the designer in the creation of an integrated view of all the sources (global schema) which is expressed in the same ODL I 3 language. We propose SI-Designer as a tool to build virtual catalogs in the E-Commerce environment.

: The purpose of semantic query optimization is to use semantic knowledge (e.g. integrity constraints) for transforming a query into a form that may be answered more efficiently than the original version. This paper proposes a general method for semantic query optimization in the framework of Object Oriented Database Systems. The method is applicable to the class of conjunctive queries and is based on two ingredients: a formalism able to express both class descriptions and integrity constraints rules as types; subsumption computation between types to evaluate the logical implications expressed by integrity constraints rules. 1 Introduction The purpose of semantic query optimization is to transform a query into an equivalent one that may be answered more efficiently than the original version. The basic idea is to use semantic knowledge about the database to transform the query. Informally, semantic equivalence means that the transformed query has the same answer as the original query o...

Abstract. Providing an integrated access to multiple heterogeneous sources is a challenging issue in global information systems for cooperation and interoperability. In the past, companies have equipped themselves with data storing systems building up informative systems containing data that are related one another, but which are often redundant, not homogeneous and not always semantically consistent. Moreover, to meet the requirements of global, Internet-based information systems, it is important that the tools developed for supporting these activities are semi-automatic and scalable as much as possible. To face the issues related to scalability in the large-scale, in this paper we propose the exploitation of mobile agents in the information integration area, and, in particular, their integration in the MOMIS infrastructure. MOMIS (Mediator EnvirOnment for Multiple Information Sources) is a system that has been conceived as a pool of tools to provide an integrated access to heterogeneous information stored in traditional databases (for example relational, object oriented databases) or in file systems, as well as in semi-structured data sources (XML-file). This proposal has been implemented within the MIKS (Mediator agent for Integration of Knowledge Sources) system and it is completely described in this paper. 1

Abstract. The SEWASIE (SEmantic Webs and AgentS in Integrated

Object-Oriented modeling and design methodologies have been receiving a significant attention since they allow a quick and easy-to-gasp overview about a complex model. However, in the literature there are no formal frameworks that allow designers to verify the consistency (absence of contradictions) of both the static and dynamic components of the specified models, that are often assumed to be consistent. In this paper, a unifying formal framework is proposed that allows the consistency checking of both the static and dynamic components of a simplified Object-Oriented model. Keywords: Object-Oriented specifications, consistency, integrity constraints, static model, dynamic model. 1

In this paper, we address the problem of consistency checking for Euclidean spatial constraints. A dimension graph representation is pmposed to maintain the Euclidean spatial constraints among objects. The basic idea is to project the spatial constraints on both X and Y dimensions, and to construct a dimension graph on each dimension. Using a dimension graph representation transfonns the problem of consistency checking into the problem of graph cycle detection. Consistency checking can be achieved with O(N+E) time as well as space complexity, where N is the number of spatial objects, and E is the number of spatial predicates in the constraint. The proposed approach is faster than O(N2) when the number of predicates is much smaller than N2 and there are few disjunctions in the spatial constraint. The dimension graph and consistency checking algorithm can be used for points, intervals and polygons in two-dimensional space. The algorithm can also guarantee global consistency.

This paper presents the use of the OLCD (Object Languages with Complements allowing Descriptive cycles) Description Logic in the modelling and design phases of industrial electrical systems. We propose the use of a DL-based system, ODB-Tools (available in internet at http://sparc20.dsi.unimo.it), to aid the developer in the design and consistency check activity of the system. ODB-Tools is an integrated environment for object oriented database (OODB) schema validation and semantic query optimization, preserving taxonomy coherence and performing taxonomic inferences. The approach of the tool is based on the OLCD description logic proposed as a common formalism to express class descriptions, a relevant set of integrity constraints (IC rules) and queries. Description Logic inference techniques are exploited to evaluate the logical implications expressed by IC rules and thus to produce the minimal taxonomy of the schema w.r.t. inheritance. ODB-Tools is a ODMG 93 [1] compliant tool, both fo...

This report discusses the barriers causing the two main problems addressed in the proposal. It also presents a detailed framework to approach the relevant and suitable solutions. 1.1