Generalized Query-By-Rule: a heterogeneous database query language (original) (raw)

An intermediate database language and its rule-based transformation to different database languages

Data & Knowledge Engineering, 1987

A user or a comptuter system which extracts information from heterogeneous DBMS faces the hard problem of dealing with different target database languages for each DBMS. We propose a solution for this problem based on an intermediate database language and its rule-based transformation to target languages. This solution is implemented in the database access module of the Intelligent Database Assistant, developed at GTE Laboratories. We describe the intermediate database language GTE DELPHI, which combines the power of relational algebra with practically important database operations, including output to a file, grouping, aggregate computations, and nested queries. We show how to convert GTE DELPHI to different relational and 4th generation database languages by a rule-based transformation system and indicate how a conversion program can be generated from examples. Translation from a high-level user language (such as English) to GTE DELPHI is simplified by using a universal relation version of GTE DELPHI as an intermediate step.

MSQL: A Multidatabase Language

Information Sciences, 1989

Many databases are now accessible through computer networks, and users frequently have data of interest in different databases. Manipulations of such data call for functions that do not exist in classical manipulation languages and database systems. A new type of data manipulation languages is needed, called multidatabase manipulation languages. We describe the multidatabase language MSQL, designed for the manipulation of data from different relational databases. MSQL is an extension of SQL, which has become the standard for relational database systems.

Semantic query processing in a heterogeneous database environment

1997

Abstract Semantic query optimization is the process of transforming a query issued by a user into a different query which, because of the semantics of the application, is guaranteed to yield the correct answer for all states of the database. While this process has been successfully applied in centralised databases, its potential for distributed and heterogeneous systems is enormous, as there is the potential to eliminate inter-site joins which are the single biggest cost factor in query processing.

Towards interoperability in heterogeneous database systems

1995

Distributed heterogeneous databases consist of systems which differ physically and logically, containing different data models and data manipulation languages. Although these databases are independently created and administered they must cooperate and interoperate. Users need to access and manipulate data from several databases and applications may require data from a wide variety of independent databases. Therefore, a new system architecture is required to manipulate and manage distinct and multiple databases, in a transparent way, while preserving their autonomy. This report contains an extensive survey on heterogeneous databases, analysing and comparing the different aspects, concepts and approaches related to the topic. It introduces an architecture to support interoperability among heterogeneous database systems. The architecture avoids the use of a centralised structure to assist in the different phases of the interoperability process. It aims to support scalability, and to assure privacy and confidentiality of the data. The proposed architecture allows the databases to decide when to participate in the system, what type of data to share and with which other databases, thereby preserving their autonomy. The report also describes an approach to information discovery in the proposed architecture, without using any centralised structure as repositories and dictionaries, and broadcasting to all databases. It attempts to reduce the number of databases searched and to preserve the privacy of the shared data. The main idea is to visit a database that either contains the requested data or knows about another database that possible contains this data.

A query mediation approach to interoperability of heterogeneous databases

Proceedings 11th Australasian Database Conference. ADC 2000 (Cat. No.PR00528), 1999

The need to transform queries between heterogeneous databases arises from many circumstances, including query transformation between a global and a local query. This paper describes a query mediation approach to the interoperability of heterogeneous databases. We develop a query mediation architecture that facilitates automated query transformation, which is applicable in many circumstances, such as query transformation in a federated database environment. Different application languages are transformed into intermediate representations that can be processed by the query mediator. The main characteristic of our system is that the query transformation agent, which acks as a mediator, is used to support automated query transformation that protects users from the troublesome task of semantic and representational discrepancies. Two query languages, ODMG-OQL and SQL have been used to investigate the query mediation architecture.

Query: The Language of Databases

Query languages have become increasingly important as comprehensive medical databases have become a part of the available knowledge base for patient care. As the user community expands and the need for bedside query arises, the requirement for a fast, easy-to-use, interactive query system must be met. This paper describes the evolution of a query language for the TMR database, discusses problems and limitations of the system, and proposes new approaches to the problem.

Typed query languages for databases containing queries

Information Systems, 1999

This paper introduces and studies the relational meta a@ebm, a statically typed extension of the relational algebra to allow for meta programming in databases. In this meta algebra one can manipulate database relations involving not only stored data values (as in classical relational databases) but also stored relational algebra expressions. Topics discussed include modeling of advanced database applications involving "procedural data"; desirability as well as limitations of a strict typing discipline in this context; equivalence with a first-order calculus; and global expressive power and non-redundancy of the proposed formalism.