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THE BUSINESS COMPONENT FACTORY

Components have been a hot topic for a couple of years now, but until recently there has been no really good book to recommend to people who want to learn more about the topic. For lack of something better, I have often recommended Clemens Szyperski's *Component Software*, but frankly it isn't a very good introduction. It's primarily a transition book, describing the differences between objects and components and comparing COM, EJB, and CORBA. More important, it doesn't provide much help with the topics we are increasingly interested in: business components and the use of components in enterprise systems design.

This deficiency has now been handsomely overcome with the publication of Peter Herzum's and Oliver Sims's new book, *Business Component Factory: A Comprehensive Overview of Component-Based Development for the Enterprise* (John Wiley & Sons, 1999, available at http://www.cutter.com/consortium/index_books.html ). I recommend this book without any qualification: This is THE book to read to understand components and the impact of components on enterprise application development. Everyone involved in architecting enterprise applications or developing component-based applications will want to read this book.

Peter Herzum is currently the director of Business Component Development for Computer Associates. Oliver Sims is a Practice Director with Genesis Development. Sims has been on the Architectural Board of the Object Management Group (OMG). (He was forced to withdraw from the board when he joined Genesis to keep Genesis from having two representatives on the board.) Both authors have been active in the OMG's business object development efforts.

A high-level table of contents provides a good overview to the scope of this book:

As you can see, this book is really about how one develops large-scale components for use in enterprise development. Until recently, talk about business components was necessarily vague: there weren't many and they were mostly approximations, without any widely accepted standards. In the past year the abstract concepts talked about by a number of practitioners have finally become concrete in the form of the OMG's new business component standards. The authors of this book have been among those who have made this happen, and thus this book is a report on the nature and structure of the latest and most important recent development in the way software will soon be architected and designed.

When you consider that, for the past year, we have had technologies like MTS and Enterprise JavaBeans, which provide delivery systems for server-size business components, but no general description of what a

business component is, or how one might go about developing an enterprise application, you realize how important *Business Component Factory* will be. This is the book that is going to introduce the upcoming generation of software developers to the concepts that weare going to rely on as we develop enterprise applications in the next decade.

Herzum and Sims define a business component as follows:

"A business component is the software implementation of an autonomous business concept or business process. It consists of all of the software artifacts necessary to represent, implement, and deploy a given business concept as an autonomous, reusable element of a larger distributed information system."

Those familiar with the move toward business components will probably find this definition unexceptional. What they will be more surprised with, however, is how Herzum and Sims proceed to extend this definition into a precise description. They define a business component, for example, as incorporating a three- or multi-tier distributed system within itself. Thus, a business component is made up of other components that fall into four groups: user interface components, workspace components that marshal information on the client, enterprise components that contain business logic and reside on the server, and resource components that manage legacy or database resources. They proceed to define each carefully, work out how one approaches developing such components and what roles they play in various architectural views.

I haven't the space to pursue the development of Herzum's and Sims's concepts in this Advisor. I'll return to specific insights in future Advisors. Meantime, however, you owe it to yourself to acquire and read this book. In a field like computing, when everything is moving so fast, it's rare to feel that you are completely up to date on any new area. Few books combine good basic definitions with up-to-the-minute developments. Reading this book provides that feeling: when you finish this book, you really do feel that you are completely up to date on component development and know where this technology is about to go next. You know that it won't last, but even feeling completely up to date for a moment is an awfully good feeling.

Till next time,

Paul Harmon

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