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Data Reverse Engineering:
Slaying the Legacy Dragon
(ISBN 0-07-000748-9)

"Anyone charged with developing a migration strategy from one application environment to another will find this book useful." - Terry Moriarty

by Peter Aiken is available now direct from a number of online bookstores including Amazon.com and McGraw-Hill (1-800-822-8158) and at neighborhood book stores. (If you are having trouble finding a copy, click here to have ACSES perform an electronic search.) This is the first book describing the process of recovering data architectures from existing information systems and using it to develop a foundation for enterprise integration and other reengineering efforts.

Forewordby Clive Finkelstein cfink@ies.aust.com

I first met Peter Aiken two years ago at a joint seminar titled "Framework for Development" that John Zachman (the originator of the Zachman Framework) and I presented in Washington, DC for IT Managers and IT staff. He was concerned that many data modeling approaches focus mainly on the future needs of organizations using Forward Engineering, such as described in my books on business-driven Information Engineering (IE), and only limited coverage was given in the literature to the discipline of Reverse Engineering. We discussed many problems that organizations have in moving their existing systems (referred to as legacy systems) to client/server environments using object-oriented techniques and development tools. Such environments generally require redevelopment of those systems.

Therein lay a dilemma: for legacy systems invariably suffer from poor or incomplete documentation. While the business rules incorporated in those systems exist in program logic, they are generally not documented in business terms. But the business users who specified those rules many years ago have since moved on, been "downsized" or otherwise discarded. Furthermore, the systems design and program documentation may also be inadequate or incomplete-or worse ... may be out of date and therefore not reliable. The IS staff who developed those systems have also moved to greener pastures, or have otherwise been "outsourced."

In our discussion we both likened this situation to two disciplines: archaeology-the study of prehistoric remains-and anthropology-the study of primitive societies. The science of reconstructing long dead civilisations from bones and other debris they left behind is often the only way to learn how they lived. With no written history, there is often no alternative but to examine and analyse those bones and debris: to determine how they were used. We can then understand what was important to them. We can learn from the past, and where relevant we can utilise that knowledge for our future. We then applied these analogies to the discipline of Reverse Engineering as it was used in the 1980s. The focus in that period was analysis of program code to determine program logic, and so business rules. Programs define HOW processing is carried out: they implement business processes. The data used by each program is apparent, but this is only a fragment of the entire data used in the business: analogous to bone fragments.

As bone fragments are difficult to comprehend until assembled into a skeleton, so also pieces of data are difficult to understand individually. But when assembled together in a data model we can see from those data fragments WHAT the business can achieve. We can then more readily determine HOW business processes work when we examine the program code. The result is clearer legacy understanding and documentation. The analysis of legacy data bases and files, and of data structures in legacy programs, enables the development of legacy data models. These data models represent the business as it was, and allow the business processes as implemented to be understood more easily. As an up-to-date plan of a house makes it easier to extend or rebuild parts of that house, so also up-to-date legacy data models enable enhancements to existing systems, or new systems, to be developed and integrated with legacy systems that will not be changed.

Peter Aiken uses the term Data Reverse Engineering to emphasize the importance of data, and to differentiate his approach from other Reverse Engineering methods. As he described the technique, I saw its power. I encouraged him to share his insights with others. This book is the result.

When I first read the finished book, it was clear he had made an important contribution. Early on he establishes the case for a focus on data. He shows the application of Data Reverse Engineering in all stages as a series of Framework Steps, using three business scenarios introduced in Chapter 1 to illustrate. His approach is impressive. The legacy data models that result enable a good understanding of existing systems to be gained, as a firm foundation then for integration into data models that address the needs for the future using Forward Engineering.

Also as you read the book, the clarity that this data focus brings to the examination of program code and data structures becomes apparent. The result is better understanding of the business rules and the business processes reflected in the legacy systems, for migration to or redevelopment in other environments. These legacy systems thus can provide clear input to their successors: legacy systems to be redeployed in new environments are clearly documented for their redevelopment. And finally, those legacy systems that must continue in their current environment can be integrated with other newer systems so they can continue to provide value to the organization.

In the years following their initial introduction into organizations, legacy systems can become essential to their operation: they are mission-critical. Data Reverse Engineering ensures that the data, information, and business rules in those systems are all fully identified so they can be incorporated, as appropriate, into the systems that replace them.

Clive Finkelstein, Managing Director
Information Engineering Services Pty Ltd
PO Box 84, Caulfield South Vic 3162 Australia
Phone: +61-3-9596-8870
Fax: +61-3-9596-1553
Internet: cfink@ies.aust.com
Compuserve: 100240,1061
Website: http://www.ies.aust.com/~ieinfo
Clive Finkelstein has over 33 years' computer experience. He is the originator of Information Engineering (IE), developed by him from 1976 and defined as "an integrated, evolutionary set of tasks and techniques that enhance business communication throughout an enterprise, enabling it to develop people, procedures, and systems to achieve its vision".

An InDepth series of six articles on Information Engineering written by Clive Finkelstein for US Computerworld in May-June, 1981 was the first IE publication worldwide: outlining both the methods and benefits of IE for business and IT. He next co-authored with James Martin the influential Savant Institute Report: "Information Engineering" published in November 1981.

These two publications started the Information Engineering Revolution of the 1980s. Over this period, IE provided dramatic quality and productivity improvement in systems development as an IS-driven variant of the methodology. This variant is now used widely by many Computer-Aided Software Engineering (CASE) tools.

In the late 80s he developed the business-driven variant of IE, linking Strategic Business Planning directly with Systems Development. He has since written extensively advancing the business-driven approach to IE with many articles and books, including: "An Introduction to Information Engineering" in 1989 and "Information Engineering: Strategic Systems Development" in 1992, both published by Addison-Wesley.

Clive is an international instructor and consultant to governments and large corporations in the USA, Australia and New Zealand, showing how information technology can be used for competitive advantage. He is a keynote speaker at conferences worldwide, and is on the International Advisory Board of DAMA International (Data Administration Management Association). He is the Founder and Chief Scientist of Information Engineering Systems Corporation in Washington, DC and is the Managing Director of Information Engineering Services Pty Ltd in Melbourne, Australia. He resides in Melbourne. Visit Clive Finkelstein's Home Page at

http://www.ozemail.com.au/~ieinfo/cbfindex.html#CBFHome.

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