Object Databases in Practice

Myths about object-oriented databases are rampant. This book debunks them, so database administrators and managers can make informed decisions about the technology.This book presents comprehensive coverage of the "pros and cons" of object-oriented databases, helping managers and administrators decide whether to implement this powerful technology. Through 18 case studies written by expert practitioners, learn how to identify the right applications for OODBMS systems, and understand the hardware requirements and technical tradeoffs involved. The book also includes many never-before-published tips, tricks and techniques for successfully designing and implementing OODBMS in your organization.All database practitioners considering object-oriented database management systems.

Introduction Today, the rate of technological change is rapidly accelerating. Organizations are faced with increasingly difficult decisions about their choices for hardware and Software platforms. Furthermore, increasing deregulation in many countries has forced companies into more aggressive deadlines and timescales to compete and survive. At present, object oriented technology is viewed as being able to deliver more reliable and better quality software, because it enables the building of more modular software by using well-defined interfaces and hiding implementation details. This can be seen in Table P-1, which shows the results of a survey of visitors to Object World UK in 1995. According to Leach Lea95, the top reason shown in Table P-1 was also number one in 1993 and 1994. The total worldwide sales of object-oriented development tools by US companies in 1995 were valued at US $1.3 Billion OOS96. A breakdown of the figures shows that object-oriented languages were the largest (US $440 Million), followed by application development environments (US $380 Million) and then object- oriented databases (US $218 Million). Object-oriented languages are quite mature; Simula (the precursor to languages such as C++) has been in existence since the late 1960s. Other languages, such as Smalltalk, have also been used for several decades. On the analysis and design side, efforts are well underway through the Object Management Group (OMG) to develop a standard modeling language to communicate object-oriented designs. The need for a standard modeling language is analogous to Electrical Engineering's need for a standard notation to communicate electrical circuit designs. A standard notation will be understood by engineers wherever they were in the world. Object databases, however, are still relatively rarely used in production LC96. The reason for this has been that a database is often at the core of many business processes within a company. Changing it can be difficult and expensive, as there may be many application dependencies. In contrast, applications can often be re- written in another language without affecting existing applications. An organization can also switch modeling languages and notions without affecting existing systems or application designs. The Growth of Object Database Usage Most of the major commercial object database products were developed towards the end of the 1980s and early 1990s. Many of them were built around object-oriented programming languages and had as their primary objective providing persistence for programming language objects. The computer-aided design vendors were early adopters of this technology. Previously, their approach was typically to store design objects in a relational database or to use some proprietary or flat file system. This approach often resulted in unsatisfactory performance. To retrieve design objects, for example, many database objects may have to be read and reassembled together in memory. For storage, the design objects would need to be flattened or decomposed to be manageable in conventional record or tuple structures. Some examples to illustrate these problems have been described by Loomis Loo95. Over the years, object database technology has become increasingly popular within other industry sectors as well. Evidence of this shift towards non-engineering applications has been reported in Lea95 and shown in Table P-2. Additional evidence showing the shift to increasing mainstream commercial usage of object databases has been reported by Barry Bar97, based on a study of twenty-four organizations. Results of another survey of 700 Information Technology (IT) professionals in DBW97 showed that nearly 50 percent of respondents indicated that object-oriented databases were a technology area that their companies may use, with the Leisure, Transport, Ret