Browsing by Author "Lawrence, Ramon"

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    AUTOMATIC INTEGRATION OF RELATIONAL DATABASE SCHEMAS
    (2000-10-16) Lawrence, Ramon; Barker, Ken
    This paper focuses on capturing the semantics of data stored in databases with the goal of integrating data sources within a company, across a network, and even on the World-Wide Web. Our approach to capturing data semantics revolves around the definition of a standardized dictionary which provides terms for referencing and categorizing data. These standardized terms are then stored in semantic specifications called X-Specs which store metadata and semantic descriptions of the data. Using these semantic specifications, it becomes possible to integrate diverse data sources even though they were not originally designed to work together. The centralized version of the architecture is presented which allows for the independent integration of data source information (represented using X-Specs) into a unified view of the data. The architecture preserves full autonomy of the underlying databases which are transparently accessed by the user from a central portal. Distributing the architecture would by-pass the central portal and allow integration of web data sources to be performed by a user's browser. Such a system which achieves automatic integration of data sources would have a major impact on how the Web is used and delivered. Unlike wrapper or mediator systems which achieve data source integration by manually defining an integrated view, our architecture automatically constructs an integrated view from information independently provided by the data sources. Thus, the contribution is an algorithm for schema integration not just a methodology for accessing data sources whose knowledge has been precombined into mediated views. The integrated view is a hierarchy of concepts that is queried by semantic name. Thus, the system provides both logical and physical access transparency by mapping user queries on high-level concepts to physical schema elements in the underlying data sources. Notes: Joint released technical report. Released as TR-00-15 for the University of Manitoba, and 2000-662-14 for the University of Calgary.
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    MULTIDATABASE QUERYING BY CONTEXT
    (2000-10-16) Lawrence, Ramon; Barker, Ken
    The overwhelming acceptance of the SQL standard \cite{Date94} has curtailed continuing research work in relational database query languages and processing. Since all commercial relational database systems conform with the SQL standard, there is little motivation for developing new query languages. Despite its benefits and wide-spread acceptance, SQL is not a perfect query language. Complex database schema challenge even experienced database users during query formulation. As increasing numbers of less sophisticated users access numerous data sources within an organization or across the Internet, their ability to accurately construct queries with the appropriate structure and semantics diminishes. SQL can be hard to use as it provides only physical access transparency not logical transparency. That is, a user is responsible for mapping the semantics of their query to the semantics and structure of the database. Although graphical tools for query construction and high-level programming languages mask some of the complexity, the notion of querying by structure is intrinsic to most forms of data access. In this work, we overview a new query language developed in conjunction with our integration architecture for automatically integrating relational schema. Although the major focus of this work is on database interoperability, the contribution of this paper is a language for specifying queries on the integrated view produced. The complexities of querying across database systems and resolving conflicts are too numerous to be fully described here, so this paper will discuss querying the integrated view of a single database. The integration architecture integrates database schema information into a context view (CV). The context view is a high-level view of database semantics which allows logically and physically transparent access to the underlying data source(s). Since this context view is an entirely new way of organizing and categorizing database information, a new query language is developed. However, we demonstrate that the context view has similar properties as the Universal Relational Model and thus can benefit from its associated algorithms and ideas. By allowing the user to query by context and semantic connotation, a whole new level of query complexity arises. Mapping of queries from semantic concepts to physical tables, fields, and relationships must be automatically performed. We will demonstrate that specific relational calculus expressions or SQL queries can be generated from abstract concepts which are rigorous enough for use in industrial applications and systems. Specifically, SQL generation and join discovery are overviewed. Thus, the query language can be mapped to SQL allowing backwards compatibility with existing systems. Notes: Joint released technical report. Released as TR-00-16 for the University of Manitoba, and 2000-663-15 for the University of Calgary.
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    ItemOpen Access
    UNITY - A DATABASE INTEGRATION TOOL
    (2000-10-16) Lawrence, Ramon; Barker, Ken
    The World-Wide Web (WWW) provides users with the ability to access a vast number of data sources distributed across the planet. Internet protocols such as TCP/IP and HTTP have provided the mechanisms for exchanging the data. However, a fundamental problem with distributed data access is the determination of semantically equivalent data. Ideally, users should be able to extract data from multiple Internet sites and have it automatically combined and presented to them in a usable form. No system has been able to accomplish these goals due to limitations in expressing and capturing data semantics. This paper details the construction, function, and deployment of Unity, a database integration software package which allows database semantics to be captured so that they may be automatically integrated. Unity is the tool that we use to implement our integration architecture detailed in previous work. Our integration architecture focuses on capturing the semantics of data stored in databases with the goal of integrating data sources within a company, across a network, and even on the World-Wide Web. Our approach to capturing data semantics revolves around the definition of a standardized dictionary which provides terms for referencing and categorizing data. These standardized terms are then stored in semantic specifications called X-Specs which store metadata and semantic descriptions of the data. Using these semantic specifications, it becomes possible to integrate diverse data sources even though they were not originally designed to work together. The centralized version of the architecture is presented which allows for the independent integration of data source information (represented using X-Specs) into a unified view of the data. The architecture preserves full autonomy of the underlying databases which are transparently accessed by the user from a central portal. Distributing the architecture would by-pass the central portal and allow integration of web data sources to be performed by a user's browser. Such a system which achieves automatic integration of data sources would have a major impact on how the Web is used and delivered. Unity is the bridge between concept and implementation. Unity is a complete software package which allows for the construction and modification of standardized dictionaries, parsing of database schema and metadata to construct X-Specs, and contains an implementation of the integration algorithm to combine X-Specs into an integrated view. Further, Unity provides a mechanism for building queries on the integrated view and algorithms for mapping semantic queries on the integrated view to structural (SQL) queries on the underlying data sources. Notes: Join released technical report. Released as TR-00-17 for the University of Manitoba, and 2000-664-16 for the University of Calgary.