Nelson Mendonca Mattos

Information integration: A research agenda

The theme for this special issue--information integration--reflects the growing importance of integration in general, and data integration in particular, as a driving force in information technology spending. This essay discusses information integration along three axes--data types, federation, and intelligence. Several important problem areas are emerging--storage and retrieval of XML (Extensible Markup Language) documents, federation and distribution across data sources, and holistic intelligence across different data modalities. This special issue is devoted to papers on many of these topics, and we expect this to be an active area of research for many years to come.

Active Database Features in SQL3

Many commercial relational database systems provide support for active rules, which are generally referred to as triggers. However, these facilities have been developed independently by different vendors, and triggers developed for one system generally do not work with another. This chapter describes how triggers are supported in the SQL3 standard, and in particular how the triggers relate to other features of the standard.

The SQL Standard

Temporal database support was added to the SQL standard in 2011. This lengthy chapter explains that support in detail and compares and contrasts it with the ideas introduced in previous chapters. It discusses “periods” (SQL’s analog of intervals, represented by explicit from/to pairs); an SQL base table can have at most one application time period (corresponding to valid time) and at most one system time period (corresponding to transaction time). SQL supports analogs of certain of the interval operators discussed in previous chapters; unfortunately, however, it has nothing analogous to PACK and UNPACK. The chapter discusses all of these operators, also database design considerations, queries, and updates in the SQL context. In particular, it explains how queries and updates work on “tables with system time” (especially system-versioned tables) and on “bitemporal tables” (tables with both application time and system time). The chapter concludes with a detailed analysis and assessment of the SQL temporal features.

Extending relational database technology for new applications

Relational database systems have been very successful in meeting the needs of todays commercial applications. However, emerging applications in disciplines such as engineering design are now generating new requirements for database functionality and performance. This paper describes a set of extensions to relational database technology, designed to meet the requirements of the new generation of applications. These extensions include a rich and extensible type subsystem that is tightly integrated into the Structured Query Language (SQL), a rules subsystem to enforce global database semantics, and a variety of performance enhancements. Many of the extensions described here have been prototyped at the IBM Database Technology Institute and in research projects at the IBM Almaden Research Center in order to demonstrate their feasibility and to validate their design. Furthermore, many of these extensions are now under consideration as part of the evolving American National Standards Institute/International Organization for Standardization (ANSI/ISO) standard for the SQL database language.

Recent design trade-offs in SQL3

SQL3 [1], the name given to the new draft of the SQL standard that is likely to become an international s tandard replacing SQL92 in 1996 or 1997, contains several object-oriented extensions [2]. When defining such extensions, X3H2 (the American Committee responsible for the specification of SQL3) and DBL (the International Committee for the same purpose) have had to make (and are still making) some of the same decisions made by the designers of other object-oriented languages. Among these decisions is the one described by Zdonik and Mater in [3]. Zdonik and Mater observed that it is not possible to combine more than three of the following four features in a single language:

Integrating information for on demand computing

Information integration provides a competitive advantage to businesses and is fundamental to on demand computing. It is strategic area of investment by software companies today whose goal is to provide a unified view of the data regardless of differences in data format, data location and access interfaces, dynamically manage data placement to match availability, currency and performance requirements, and provide autonomic features that reduce the burden on IT staffs for managing complex data architectures. This paper describes the motivation for integrating information for on demand computing, explains its requirements, and illustrates its value through usage scenarios. As shown in the paper, there is still a tremendous amount of research, engineering, and development work needed to make the full information integration vision a reality and it is expected that software companies will continue to heavily invest in aggressively pursing the information integration vision.

Object-relational database systems (tutorial): principles, products and challenges

Object-relational database systems, a.k.a. “universal servers,” are emerging as the next major generation of commercial database system technology. Products from relational DBMS vendors including IBM, Informix, Oracle, UniSQL, and others, include object-relational features today, and all of the major vendors appear to be on course to delivering full object-relational support in their products over the next few years. In addition, the SQL3 standard is rapidly solidifying in this area. The goal of this tutorial is to explain what the key features are of object-relational database systems, review what todays products provide, and then look ahead to where these systems are heading. The presentation will be aimed at general SIGMOD audience, and should therefore be appropriate for users, practitioners, and/or researchers who want to learn about object-relational database systems.

From Object-Relational to Federated Databases

Object-relational databases allow users to manipulate rich data types that are not supported by traditional relational database systems. However, the majority of such data are in systems that are outside of that database—either in file systems, specialized systems, hierarchical databases, or other varieties of relational database that do not provide as rich a level of abstraction. Users want to take advantage of object-relational technology to exploit the rich semantics and abstraction but cannot afford to change existing applications or to move that data into the database to do so. The solution for enterprises is a federated database system, which allows users to leverage their existing applications and existing data, while allowing new applications to exploit the functional richness of object-relational technology.

Enhancing knowledge processing in client/server environments

A great variety of techniques has been developed to optimize and enhance query processing for relational, client/server, distributed, parallel, and heterogeneous database systems (DBS). Based on that work and experience, we investigate how far those techniques are applicable to query processing in Knowledge Base Management Systems (KBMS). Our reference system is the KRISYS KBMS that consists of a knowledge-processing system at the client (clientbased processing) and a data-processing system at the server (database backend). We describe a unifying framework for query processing incorporating both processing systems (as realized in KRISYS). This allows to distribute and balance the amount of work done in the client and in the server. Based on an evaluation of that framework, several approaches to further enhance knowledge processing are reported.

O-O, what's happening to DB2?

In this presentation, we will describe a collection of new object-relational features that have been added to IBMs DB2 Universal Database (UDB) system. The features to be described include support for structured types, object references, and hierarchies of typed tables and views. These features will be covered from the perspective of a database designer or end user. In addition to presenting the features presently available in DB2 UDB V5.2, which became available in Fall 1998, we will discuss the expected evolution and impact of this technology over time.