Multidatabase Language Research Articles

A Graphical Interface to Genome Multidatabases

Formulating queries to access multiple databases can be a formidable task especially when many terms from various databases and complex constraints are involved. To specify a multidatabase query, the user usually has to search through documents for exact database terms and learn the multidatabase language. This report presents QUICK (QUery Interface to CPL-Kleisli), a graphical user interface to multiple databases. CPL (Collection Programming Language) is a high-level multidatabase language built on top of an open query system Kleisli. QUICK allows users to handle overwhelming information from different data sources in an intuitive and uniform manner. The query specification is reduced to specifying user’s terms in his/her own world, selecting paths and specifying constraints in a graph. QUICK is able to automatically generate a CPL query that corresponds to the user’s intent. Additional graphical functions are provided for the user to fine-tune the query generated.

A HYPERRELATIONAL APPROACH TO INTEGRATION AND MANIPULATION OF DATA IN MULTIDATABASE SYSTEMS

The issue of interoperability among multiple autonomous databases has attracted a lot of attention from researchers in these years. The past research on this issue can be roughly divided into two main categories: the tightly-integrated approach that integrate databases by building an integrated schema and the loosely-integrated approach that achieves interoperability by using a multidatabase language. Most of the past efforts focused on the issues in the first approach. The problem with the first approach is, however, that it lacks a convenient representation of the integrated schema at the system level and a sound mathematical basis for data manipulation in a multidatabase system. In this paper, we propose to use hyperrelations as a powerful and succinct model for the global level representation of heterogeneous database schemas. A hyperrelation has the structure of a relation, but its contents are the schemas of the semantically equivalent local relations in the databases. With this representation, the metadata of the global database, local databases and the data of these databases are all representable by using the structure of a relation. The impact of such a representation is that all the elegant features of relational systems can be easily extended to multidatabase systems. A hyperrelational algebra is designed accordingly. This algebra is performed at the multidatabase systems (MDBS) level such that query transformation and optimization is supported on a sound mathematical basis. The major contributions of this paper include: (1) Local relations of various schemas (even though they retain information of the same semantics) can be systematically mapped to hyperrelations. As the structure of a hyperrelation is similar to that of a relation, data manipulation and management tasks (such as design of the global query language and the view mechanism) are greatly facilitated. (2) The hyperrelational algebra provides a sound basis for query transformation and optimization in a MDBS.

Multidatabase interoperability in the Jupiter system

This article proposes a model for multidatabase interoperability whereby a formal model and multidatabase language of Jupiter ∗ ∗ Partially funded under the ESPRIT Programme of the Commission of the European Union as part of the EDITH Project 7507, European Distributed Information Technology for Healthcare. are introduced and the formal semantics of the multi-database language is defined in terms of the formal model. The development of the model is incremental in approach, starting with relational model semantics and extending this semantics to a multirelational model. Due to space requirements we only outline the multirelational part of our work and take the single relational part as given. The contribution of this article is that it defines a uniform formal framework for the investigation of properties of multidatabase systems and their languages. An architecture and implementation language are defined and a CORBA-based prototype: the Jupiter Interoperator, is discussed. Legacy systems are characterized in this article along three related dimensions: the legacy applications themselves; the subsystems which support the legacy applications and interoperability; and the models and languages of the legacy applications and subsystems.

On resolving schematic heterogeneity in multidatabase systems

The objective of a multidatabase system is to provide a single uniform interface to accessing multiple independent databases being managed by multiple independent, and possibly heterogeneous, database systems. One crucial element in the design of a multidatabase system is the design of a data definition language for specifying a schema that represents the integration of the schemas of multiple independent databases. The design of such a language in turn requires a comprehensive classification of the conflicts (i.e., discrepancies) among the schemas of the independent databases and development of techniques for resolving (i.e., homogenizing) all of the conflicts in the classification. An earlier paper provided a comprehensive classification of schematic conflicts that may arise when integrating multiple independent relational database (RDB) schemas into a single multidatabase (MDB) schema. In this paper, we provide a comprehensive classification of techniques for resolving the schematic conflicts that may arise when integrating multiple RDB schemas, or RDB schemas and object-oriented database (OODB) schemas, or multiple OODB schemas. The classification of conflict resolution techniques includes not only those necessary for resolving schematic conflicts identified in the earlier paper, but also additional conflicts that arise when OODBs become part of the databases to be integrated. Most of the conflict resolution techniques discussed in the paper have already been incorporated into SQL/M, a multidatabase language implemented in UniSQL/M, a commercially available multidatabase system from UniSQL, Inc. which integrated SQL-based relational database systems and the UniSQL/X unified relational and object-oriented database system.

A taxonomy and current issues in multidatabase systems

A taxonomy of global information-sharing systems is presented, and the way in which multidatabase systems fit into the spectrum of solutions is discussed. The taxonomy is used as a basis for defining multidatabase systems. Issues associated with multidatabase systems are reviewed. Two major design approaches for multidatabases, global schema systems and multidatabase language systems, are described. Existing multidatabase projects and areas for further research are also discussed. >

MSQL: A multidatabase language

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.