This book begins with a quick glance at today's n-tiered architectures and where Microsoft's Distributed Internet Architecture (DNA) fits in. Instead of a quick fix, the authors suggest that multitiered architectures bring in new design considerations. They provide advice for "balancing the tiers" in order to create maintainable, robust applications.

The book also adequately covers adding persistence to distributed Component Object Model (DCOM) components and how to manage monikers for simplifying access to remote objects. Further sections look at DCOM event handling (and connection points) and furnish explanations of DCOM's threading models, including the use of synchronization objects. Material on using the Windows Registry will help demystify the way DCOM stores component information. The authors look at building DCOM objects with aggregation (which mimics inheritance). Additional advanced topics here include Windows NT services, marshalling, security, and error handling.

The most useful chapters here concentrate on MTS for transaction support and MSMQ for adding message delivery to custom applications. The authors discuss both administration and programming issues, including tools like the MTS Explorer. (Included here is a useful chapter on Microsoft's COM Transaction Integrator [COMTI] mainframe tool.) For MSMQ development, the authors look at both the MSMQ Library API and ActiveX components, which let programmers add message support to their DCOM components. The book closes with some useful material on Microsoft's emerging COM+ standard.

With its grab bag of advanced DCOM topics, this book will be most useful to those readers with a previous understanding of the Active Template Library (ATL) and DCOM. That said, COM/DCOM Unleashed can certainly deepen your knowledge of DCOM and let you write C++/ATL components that make better use of Microsoft's DNA platform. --Richard Dragan