Tlus paper demonskates that a snnple rule system can be constructed that supports a more powerful view system than avadable 111 current commercial systems Not only can views be spectied by usmg rules but also special semantics for resolvmg ambiguous view updates are sunply addltlonal rules Moreover, procedural data types as proposed m POSTGRES are also efficiently sunulated by the same rules system Lastly, cachmg of the actlon part of certam rules 1s a possible performance enhancement and can be apphed to matenallze views as well as to cache procedural data items Hence, we conclude that a rule system IS a fundamental concept m a next generation DBMS, and it subsumes both views and procedures as special cases 1 INTRODUCTION

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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.Integration is the driving force of this decade of IT (information technology) spending. As enterprises buy more and more packaged applications, it is estimated that the task of combining these application "silos" results in over 40 percent of the IT spending, even though the amount of code written for integration is significantly smaller than 40 percent. This is because integration projects tend to be one-of-akind, and complex to write. The question for software and services vendors is this: can the cost of integration be reduced to be more in line with that of packaged applications?The essay is organized as follows. This section describes four integration models. The next section gives an overview of information integration. Following sections then explore some of the technical challenges along the three axes that are the basis for our model of information integration. Finally, we end with some conclusions.There are four distinct forms of integration: 1. Portals (or "at-the-glass") integration is the shallowest form, bringing potentially disparate applications together in a (typically Web) single entry point. 2. Business-process integration orchestrates processes across application and possibly enterprise boundaries, such as those involved in a supplychain relationship. Web services and their derivatives are becoming important here. 3. Application integration, in which applications that do similar or complementary things communicate with each other, is typically focused on data transformation and message queuing, increasingly in the XML (Extensible Markup Language) domain. 4. Information integration, wherein complementary data are either physically (through warehousing tools) or logically brought together, makes it possible for applications to be written to and make use of all the relevant data in the enterprise, even if the data are not directly under their control. A typical example of this would be a new customer relationship application that combines the relational call log with the speech-to-text translated call itself.

The rate of increase in database size and response time requirements has outpaced advancements in processor and mass storage technology. One way to satisfy the increasing demand for processing power and I/O bandwidth in database applications is to have a number of processors, loosely or tightly coupled, serving database requests concurrently. Technologies developed during the last decade have made commercial parallel database systems a reality and these systems have made an inroad into the stronghold of traditionally mainframe based large database applications. This paper describes the parallel database project initiated at IBM Research at Hawthorne and the DB2/AIX-PE product based on it.