IIOP Complete: Understanding CORBA and Middleware Interoperability

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PREFACE:

The Importance of Middleware and Interoperability

The development of applications in business enterprises has been fundamentally altered by two strong desires. The first is to be able to develop new software as components, thereby allowing their reuse. The second is to be able to create new applications by integrating legacy systems, databases, and components with new packaged or Internet applications in very short time frames. Middleware is the name given to a breed of software that allows component technology to be developed and integrated into new applications. The software industry has rushed to fill this need by providing a wide variety of middleware technologies. Much of what has been available is proprietary to a specific vendor, thereby locking a developer into its solution. However, this has been changing through the efforts of groups such as the Object Management Group (OMG) that have provided a forum for the creation of middleware standards.

Most enterprise information systems contain a diversity of technology in their operational systems. Being tied to any single vendor puts an enterprise at a disadvantage because no one can accurately predict the demands that it will have for the next generation of applications. The Internet will be a critical component of every major enterprise in the future, and the nature of its design and usage requires that an organization support diversity.

The Common Object Request Broker Architecture (CORBA) is a standard for distributed object middleware created by the OMG. The Internet Inter-ORB Protocol (IIOP) is one of the standards created by the OMG. IIOP was established to allowinteroperability of CORBA middleware and distributed components. It has become widely adopted by many software vendors and embedded into their products.

This book is about the state of middleware technology, focusing on the issue of interoperability. Middleware evolution will continue at an ever increasing pace, with an emphasis on distributed objects and components. Interoperability will be demanded by developers to ease their burdens in integrating together distributed components and applications and IIOP will play an important role in solving this problem.

The IIOP specification is an extremely simple and concise document. However, it is only a description of the standard. By itself, it doesn't aid the reader in acquiring a deeper understanding of the technology. This book is intended to provide the reader with an understanding of the IIOP standard and its usage. It is aimed at readers who currently use or will use technologies that employ IIOP. It can help the network engineer understand the effect of the protocol, the programmer to make better design decisions, and the integrator to help non-object systems integrate with object-based systems.

To thoroughly understand IIOP, one must view it from three perspectives. The first is technical, including a treatment of the standard, examples, and considerations related to implementation. The second is interoperability, to examine potential configurations in which IIOP can be applied. The third is business, to understand how IIOP fits into the marketplace and the level of acceptance it has and might achieve.

The authors have each been involved with object technology from both a system integration and product development perspective. Through these experiences, we have used a variety of competing technologies as well as applied IIOP-based technology to new systems and applications. This book will help the reader develop interoperable solutions using IIOP.

Overview of Contents

Part 1 provides a solid discussion of IIOP and its place in the world. It is aimed at the reader who does not understand middleware and its evolution. Chapter 1 touches on most aspects of IIOP, giving a quick peek at the book's contents. Chapter 2 gives a broad understanding of the current state of middleware technology. At the end of Part 1, the reader should understand the world of middleware, with an emphasis on the CORBA and IIOP standards.

Part 2 is a detailed discussion of the IIOP standard. Chapter 3 describes the OMG standards process that established IIOP. It describes IIOP's message formats, data representations, and transport requirements in Chapters 4 and 5. Chapter 6 explains how several CORBA ORBs have implemented IIOP. All aspects of the standard are addressed in detail, as well as the latest changes to the standard in Chapter 7. These changes will find themselves in the next generation of CORBA-based products.

Part 3 discusses advanced topics related to IIOP. This includes a description in Chapter 8 of the role of security in middleware as well as how it can be accomplished using IIOP. Other topics addressed in Chapters 9 and 10 are how to build interoperable solutions, the fit of IIOP into Java and the Web, and the future of IIOP.

Acknowledgments

The process of writing a book requires a significant amount of support from many people. This support comes in the form of reviews, discussion, encouragement, organization, and coordination. We were fortunate to have support from a wide variety of friends, associates, and other characters. We wish to thank all of them for being there at our moments of need. We especially want to thank Bret Hartman, Barry Horowitz, Frank Maginnis, Raphael Malveaux, John Marsh, Thomas Mowbray, Makoto Oya, Aarthi Prasad, Karen Ruh, Takaaki Shigematsu, Kim Warren, Eric Watson, Julie Vazquez, Robert Vazquez, and Ron Zahavi.

We are extremely proud to be associated with Addison-Wesley and our editor Carter Shanklin. They have provided us two outstanding people in Krysia Bebick and Kristin Erickson who made the process of writing this book a lot easier. The production coordinator, Jacquelyn Doucette, deserves special thanks and has our appreciation for helping produce a quality product. Laura Michaels's copyediting was a work of art by itself.

Special thanks is given to the reviewers of the book whose comments and invaluable insights significantly increased its quality. We specifically want to acknowledge John M. Anderson, Boeing; Dave Curtis; Naci Dai; Fred Hebbel, CTO, SYSNETICS; Glen Jones, Raytheon E-Systems; Dr. Christopher LoPresti; Robert Stodola, SmithKline Beecham Pharmaceuticals R&D; Dave Tropeano; and Alan L. Pope, Quantitative Data Systems, Inc.

Finally, we thank Elizabeth (Liz) May, who organized and coordinated the manuscript among all parties. Her support and efforts on this book were very important to getting it to completion. We thank her for helping to "herd the cats" home!

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