Conflictfreeness as a basis for schema integration

2008

* Supported by Bell Canada through the Bell University Labs, NSERC and Ontario Centres Of Excellence markable duality between them. The results of the paper can then be seen as an (important yet) particular case of this general duality theory. Contents 3 Sample scenario 3.1 Example of relational schema integration

2001

Interoperability and integration of data sources are becoming ever more important issues as both, the amount of data and the number of data producers are growing. Interoperability not only has to resolve the differences in data structures, it also has to deal with semantic heterogeneity. Semantics refer to the meaning of data in contrast to syntax, which only defines the structure of the schema items (e.g., classes and attributes). We focus on the part of semantics related to the meanings of the terms used as identifiers in schema definitions. This paper presents an approach to integrate schemas from different communities, where each such community is using its own ontology. The approach is based on merging ontologies based on similarity relations among concepts of different ontologies. We present formal definitions of similarity relations based on intensional definitions and conclude the extensional consequences. The process of merging ontologies based on the detected similarity relations is discussed. The merged ontology is finally used to derive an integrated schema. The resulting schema can be used as the global schema in a federated database system.

2001

Interoperability and integration of data sources are becoming ever more important issues as both, the amount of data and the number of data producers are growing. Interoperability not only has to resolve the differences in data structures, it also has to deal with semantic heterogeneity. Semantics refer to the meaning of data in contrast to syntax, which only defines the structure of the schema items (e.g., classes and attributes). We focus on the part of semantics related to the meanings of the terms used as identifiers in schema definitions. This paper presents an approach to integrate schemas from different communities, where each such community is using its own ontology. The approach is based on merging ontologies based on similarity relations among concepts of different ontologies. We present formal definitions of similarity relations based on intensional definitions and conclude the extensional consequences. The process of merging ontologies based on the detected similarity relations is discussed. The merged ontology is finally used to derive an integrated schema. The resulting schema can be used as the global schema in a federated database system.

Data & Knowledge Engineering, 1998

Schema integration is an important discipline for constructing a heterogeneous database system, since there exists various semantic discrepancies among local schemas. However, prior works rarely address the problems of integrating local relations with conflicts of different schema structures. In this paper, we propose an approach for the integration of local relations with such conflicts. In our approach, we define some auxiliary data called metadata for local schemas. The relations can be classified into some classes according to the metadata. The local relations with conflicts of different schema structures are respectively transformed to new relations with the same structure. Finally, we integrate these new relations. We also explore the query decomposition process for global queries. A global query is decomposed into many local queries according to the local schemas' structures. The results of the local queries will be sent to the global site. Finally, the global site integrates the local results into a new one and poses the global query on the integrated result again to get the final result. Since this process filters out unnecessary data in each local site, it can also be regarded as an important work for global query optimization.

I want to thank my family for being supportive over all these years, especially my beautiful wife, Carri, and my mother, Gloria. I would also like to recognize the tireless efforts of my supervisor, Dr. Ken Barker, and the committee for evaluating this work. Finally, I am very appreciative to funding agencies such as NSERC, TRLabs, and the University of Manitoba whose financial support made this thesis possible.

Information Technology & Management, 2005

This paper addresses the problem of handling semantic heterogeneity during database schema integration. We focus on the semantics of terms used as identifiers in schema definitions. Our solution does not rely on the names of the schema elements or the structure of the schemas. Instead, we utilize formal ontologies consisting of intensional definitions of terms represented in a logical language. The approach is based on similarity relations between intensional definitions in different ontologies. We present the definitions of similarity relations based on intensional definitions in formal ontologies. The extensional consequences of intensional relations are addressed. The paper shows how similarity relations are discovered by a reasoning system using a higher-level ontology. These similarity relations are then used to derive an integrated schema in two steps. First, we show how to use similarity relations to generate the class hierarchy of the global schema. Second, we explain how to enhance the class definitions with attributes. This approach reduces the cost of generating or re-generating global schemas for tightly-coupled federated databases.

2001

Abstract Research in the area of data integration has resulted in approaches such as federated and multidatabases, mediation, data warehousing, global information systems, and the model management/schema matching approach. Architecturally, approaches can be categorized into those that integrate against a single global schema and those that do not, while on the level of inter-schema constraints, most work can be classied either as so-called global-as-view or as local-as-view integration.

Advances in Conceptual Modeling-Theory and …, 2006

Three themes are apparent in recent schema integration, evolution and versioning research. First, the need to reduce the number of schema changes that are necessary. The approach here has been to build into the conceptual and data models the scope to accommodate modest changes to definition. Second, research that aims to reuse the current schema definition through procedures that mask the changes through sophisticated wrappers or techniques for multiple extensional data. Finally, techniques that enable schema change to be accommodated as seamlessly and as painlessly as possible. All these approaches have their limitations and strengths. This paper investigates each of these approaches and outlines the current research directions in schema integration, evolution and versioning.

Three themes are apparent in recent schema integration, evolution and versioning research. First, the need to reduce the number of schema changes that are necessary. The approach here has been to build into the conceptual and data models the scope to accommodate modest changes to definition. Second, research that aims to reuse the current schema definition through procedures that mask the changes through sophisticated wrappers or techniques for multiple extensional data. Finally, techniques that enable schema change to be accommodated as seamlessly and as painlessly as possible. All these approaches have their limitations and strengths. This paper investigates each of these approaches and outlines the current research directions in schema integration, evolution and versioning.

Data & Knowledge Engineering, 2004

Conflict detection and analysis are of high importance, e.g., when integrating conceptual schemata, such as UML-Specifications, or analysing goal-fulfilment of sets of autonomous agents. In general, models for this introduce unnecessarily complicated frameworks with several disadvantages regarding semantics as well as complexity. This paper demonstrates that an important set of static and dynamic conflicts between specifications can be diagnosed using ordinary first-order modal logic. Furthermore, we show how the framework can be extended for handling situations when there are convex sets of probability measures over a state-space. Thus, representing specifications as conceptual schemata and using standard Kripke models of modal logic, augmented with an interval-valued probability measure, we propose instrumental definitions and procedures for conflict detection.