Distributed Heterogeneous Data Access

The huge number of autonomous and heterogeneous data repositories accessible on the "global information infrastructure" makes it impossible for users to be aware of the locations, structure/organization, query languages and semantics of the data in various repositories. There is a critical need to complement current browsing, navigational and information retrieval techniques with a strategy that focuses on information content and semantics. In any strategy that focuses on information content, the most critical problem is that of different vocabularies used to describe similar information across domains. We discuss a scalable approach for vocabulary sharing. The objects in the repositories are represented as intensional descriptions by pre-existing ontologies expressed in Description Logics characterizing information in different domains. User queries are rewritten by using interontology relationships to obtain semanticspreserving translations across the ontologies.

The huge number of autonomous and heterogeneous data repositories accessible on the "global information infrastructure" makes it impossible for users to be aware of the locations, structure/organization, query languages and semantics of the data in various repositories. There is a critical need to complement current browsing, navigational and information retrieval techniques with a strategy that focuses on information content and semantics. In any strategy that focuses on information content, the most critical problem is that of different vocabularies used to describe similar information across domains. We discuss a scalable approach for vocabulary sharing. The objects in the repositories are represented as intensional descriptions by pre-existing ontologies expressed in Description Logics characterizing information in different domains. User queries are rewritten by using interontology relationships to obtain semanticspreserving translations across the ontologies.

The huge number of autonomous and heterogeneous data repositories accessible on the "global information infrastructure" makes it impossible for users to be aware of the locations, structure/organization, query languages and semantics of the data in various repositories. There is a critical need to complement current browsing, navigational and information retrieval techniques with a strategy that focuses on information content and semantics. In any strategy that focuses on information content, the most critical problem is that of different vocabularies used to describe similar information across domains. We discuss a scalable approach for vocabulary sharing. The objects in the repositories are represented as intensional descriptions by pre-existing ontologies expressed in Description Logics characterizing information in different domains. User queries are rewritten by using interontology relationships to obtain semanticspreserving translations across the ontologies.

Considerable progress has been achieved in the area of virtual database systems, but substantial problems still persist. In this paper we discuss two current research directions: The resolution of extensional inconsistencies among databases participating in a virtual database, and the automatic incorporation of new information sources based on a process of discovery. Our approach to both problems involves to some degree what is often referred to as soft computing techniques. 1

Considerable progress has been achieved in the area of virtual database systems, but substantial problems still persist. In this paper we discuss two current research directions: The resolution of extensional inconsistencies among databases participating in a virtual database, and the automatic incorporation of new information sources based on a process of discovery. Our approach to both problems involves to some degree what is often referred to as soft computing techniques.

The World Wide Web is fast becoming a ubiquitous computing environment. Prevalent keyword-based search techniques are scalable, but are incapable of accessing information based on concepts. We investigate the use of concepts from multiple, real-world pre-existing, domain ontologies to describe the underlying data content and support information access at a higher level of abstraction. It is infeasible to expect a single domain ontology to describe the vasts amounts of data on the web. In fact we expect multiple ontologies to be used as di erent world views and present an approach to \browse" ontologies as a paradigm for information access. A critical challenge in this approach is the vocabulary heterogeneity problem. Queries are rewritten using interontology relationships to obtain translations across ontologies. However, some translations may not be semantics preserving, leading to uncertainty or loss in the information retrieved. We present a novel approach for estimating loss of information based on navigation of ontological terms. We de ne measures for loss of information based on intensional information as well as on well established metrics like precision and recall based on extensional information. This measures are used to select results of the desired quality of information.

Recent emerging technologies such as internetworking and the World Wide Web (WWW) have signi cantly expanded the types, availability, and volume of data accessible to an information management system. In this new environment it is imperative to view an information source at the level of its relevant semantic concepts. We propose that these semantic concepts be chosen from pre-existing domain speci c ontologies. Domain speci c ontologies are used as tools/mechanisms for specifying the ontological commitments or agreements between information users and providers on the information infrastructure. We use domain speci c ontologies to tackle the information explosion by the: (a) Re-use and organization of knowledge in pre-existing real world ontologies, achieved by mapping semantic concepts in the ontologies to data structures in the underlying repositories; and (b) Knowledge integration and development of mechanisms to translate information requests across ontologies. We thus provide support for multiple domain speci c ontologies as alternate world views on the vast amounts of data. Semantic information brokering is implemented by brokering across domain ontologies based on interontology relationships such as synonyms, hyponyms and hypernyms de ned between terms in di erent ontologies. Information requests are rewritten using these relationships to obtain translations across ontologies. These ideas have been implemented in the OBSERVER system, the algorithms for which are discussed in this paper.

The World Wide Web is fast becoming a ubiquitous computing environment. Prevalent keyword-based search techniques are scalable, but are incapable of accessing information based on concepts. We investigate the use of concepts from multiple, real-world pre-existing, domain ontologies to describe the underlying data content and support information access at a higher level of abstraction. It is infeasible to expect a single domain ontology to describe the vasts amounts of data on the web. In fact we expect multiple ...

Recent emerging technologies such as internetworking and the World Wide Web (WWW) have signi cantly expanded the types, availability, and volume of data accessible to an information management system. In this new environment it is imperative to view an ...

There has been an explosion in the types, availability and volume of data accessible in an information system, thanks to the World Wide Web (the Web) and related inter-networking technologies. In this environment, there is a critical need to replace or complement earlier database integration approaches and current browsing and keyword-based techniques with concept-based approaches. Ontologies are increasingly becoming accepted as an important part of any concept or semantics based solution, and there is increasing ...

This paper addresses the development o f a c ooperative database system, called Distributed Object Kernel DOK, which provides computation over heterogeneous databases. The DOK logical architecture has a clear separation of concerns, and involves a coordination layer, a task layer and a database layer. Each of these layers contains a set of agents which are specialised in performing speci c functions related to the cooperative computation. When a user requests or queries information about a DOK application, the coordination agents identify and delegate the subparts of the query to appropriate agents of the task-based layer. The specialised agents in turn, use the agents of the database layer to access the required information to process the di erent sub-parts of the global request. One of the important agents in the DOK environment is the wrapper coordination agent. A wrapper performs some advanced functions on behalf of the DOK manager, including i the re-engineering function which allows the understanding and the discovery of the semantics embedded in local heterogeneous databases, ii the security function which allows di erent levels of autonomy to be supported e.g. strongly coupled to loosely coupled systems, and iii the reliability function which provide a reliable cooperative e n vironment for information sharing.

The World Wide Web is fast becoming a ubiquitous computing environment. Prevalent keyword-based search techniques are scalable, but are incapable of accessing information based on concepts. We investigate the use of concepts from multiple, real-world preexisting, domain ontologies to describe the underlying data content and support information access at a higher level of abstraction. It is infeasible to expect a single domain ontology to describe the vasts amounts of data on the web. In fact we expect multiple ontologies to be used as different world views and present an approach to "browse" ontologies as a paradigm for information access. A critical challenge in this approach is the vocabulary heterogeneity problem. Queries are rewritten using interontology relationships to obtain translations across ontologies. However, some translations may not be semantics preserving, leading to uncertainty or loss in the information retrieved. We present a novel approach for estimatin...

Abstract: Recent emerging technologies such as internetworking and the World WideWeb (WWW) have significantly expanded the types, availability, and volumeof data accessible to an information management system. In this new environmentit is imperative to view an information source at the level of its relevantsemantic concepts. We propose that these semantic concepts be chosen frompre-existing domain specific ontologies. Domain specific ontologies

Recent emerging technologies such as internetworking and the World Wide Web (WWW) have signi cantly expanded the types, availability, and volume of data accessible to an information management system. In this new environment it is imperative to view an ...

There has been an explosion in the types, availability and volume of data accessible in an information system, thanks to the World Wide Web (the Web) and related inter-networking technologies. In this environment, there is a critical need to replace or complement earlier database integration approaches and current browsing and keyword-based techniques with concept-based approaches. Ontologies are increasingly becoming accepted as an important part of any concept or semantics based solution, and there is increasing ...

There has been an explosion in the types, availability and volume of data accessible in an information system, thanks to the World Wide Web (the Web) and related inter-networking technologies. In this environment, there is a critical need to replace or complement earlier database integration approaches and current browsing and keyword-based techniques with concept-based approaches. Ontologies are increasingly becoming accepted as an important part of any concept or semantics based solution, and there is increasing realization that any viable solution will need to support multiple ontologies that may be independently developed and managed. In particular, we consider the use of concepts from pre-existing real world domain ontologies for describing the content of the underlying data repositories. The most challenging issue in this approach is that of vocabulary sharing, which involves dealing with the use of different terms or concepts to describe similar information. In this paper, we describe the architecture, design and implementation of the OBSERVER system. Brokering across the domain ontologies is enabled by representing and utilizing interontology relationships such as (but not limited to) synonyms, hyponyms and hypernyms across terms in different ontologies. User queries are rewritten by using these relationships to obtain translations across ontologies. Well established metrics like precision and recall based on the extensions underlying the concepts are used to estimate the loss of information, if any.

Abstract The World Wide Web is fast becoming a ubiquitous computing environment. Prevalent keyword-based search techniques are scalable, but are incapable of accessing information based on concepts. We investigate the use of concepts from multiple, real-world pre-existing, domain ontologies to describe the underlying data content and support information access at a higher level of abstraction. It is infeasible to expect a single domain ontology to describe the vasts amounts of data on the web.

ABSTRACT In this paper, we discuss how ontologies can represent and handle enormous and heterogeneous information in order to organize information according to our intention. We discuss ontologies from two points of view in this paper. One is how to formalize ontologies that can represent multiple definitions for concepts. We propose to formalize ontologies by aspects and discussed its nature. The other is how ontologies can work to deal with information.