CRC Card Book, The

Applying the object-oriented paradigm to the development of software requires individuals and teams to think and act differently than when designing procedural projects. While proponents of the object paradigm often say identifying objects is a simple and intuitive process, experienced developers know that this is not always true. The solution is the CRC (Classes, Responsibilities, Collaboration) Card method, a proven technique for identifying classes and visualizing and testing different class-based models during the design phase.

The CRC Card Book covers the CRC method from start to finish, illustrating its application in three different in-depth case studies which supply tips and pointers drawn from real world experience. The case studies are presented in the engaging style of a novella to demonstrate how personalities and organizational culture come into play when using the CRC technique. C++, Java, and Smalltalk experts provide implementation examples in each language. The CRC Card Book demonstrates how to:

• Discover classes through team brainstorming
• Refine project requirements
• Test the conception of the system and evaluate potential paths of collaboration using role play
• Manage an object-oriented project
• Implement a CRC design in C++, Java, and Smalltalk; all source code is available via the World Wide Web.

Includes language implementation examples from such noted experts as:

• Java: Cay Horstman, San Jose State University
  
• Smalltalk: Larry Smith, IBM Corp.
  
• C++: Jeremy Raw, Interactive Software
  

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Praise For CRC Card Book, The

"Thank you both for producing a book on CRC that I can recommend to anyone who wants to understand not only how to use the CRC method but also the dynamics of the team approach to software design. If your goal is better software design this book will help you achieve it."

Ward Cunningham

Inventor, CRC Card Technique

Cunningham & Cunningham, Inc.

"David and Susan have captured much of the spirit of sharing, thinking, and communicating that CRC was originally invented for...[This book] is a significant contribution to the literature, not just of CRC, but of what it means for teams to develop objects--really what it means for teams to develop."

Kent Beck

"Great, wonderful, stupendous! This insightful book provides valuable information and examples which can be used on real projects, rather than dry discussions of theoretical aspects of object-oriented analysis. I would immediately recommend that the people and projects I consult with purchase the book!"

Charles Snyder

Rational Software Corp.

Preface

Applying the object-oriented paradigm in the development of software applications requires the individual developer and the application team to think and act quite differently than one would in approaching a procedures based project. Object-oriented projects follow a new software development life cycle, one that is both iterative and incremental, a cyclic spiral of analysis, design, and deployment. In this new application-development process, determining and defining properly the classes that are central to the desired system at the beginning of the life cycle is critical. Thorough analysis of the problem and good design up front saves time, and money and helps ensure a successful end result.

Although proponents of the object paradigm often say that identifying objects is a simple and intuitive process, a number of noted experts admit that this is not always true! Particularly with larger-scale applications, omitting a formal analysis of the base classes necessary to the application and the related analysis of their responsibilities and collaboration is certain to lead to missed schedules, blown budgets, and frayed nerves. The solution is to use the CRC process to determine the classes necessary to the system as part of the design process for the application. CRC (classes, responsibility, and collaboration) cards can be used to visualize and test different class-based models during the design phase. It is a proven technique used and advocated by leading methodologists.

The CRC Card Book demonstrates the use of the CRC methodology in a realistic team setting, covering the full range this methodology from initial identification of classes to the production of code based on these classes. At this writing, there are two other books on or incorporating coverage of CRC. Rebecca Wirfs-Brock wrote Designing Object-Oriented Software many years ago. It remains the classic definition of responsibility-driven design, but does not discuss the application of the technique in the team-oriented setting in which large-scale applications are developed. Nancy Wilkinson's book, Using CRC Cards, focuses specifically on the C++ programming community and likewise does not include any illustration of the team approach to class discovery.

The approach of The CRC Card Book is to cover the CRC method from start to finish, demonstrating its application in three different, detailed case-study examples while supplying tips and pointers throughout. The book demonstrates how real teams can use the CRC technique to accomplish a variety of tasks, including:

• Initially discovering classes

• Selecting the core classes

• Acting out class relationships and scenarios

• Refining the project requirements

• Furthering project management

• Serving as a guide to the design of code (in C++, Java, and Smalltalk)

The CRC Card Book is organized as follows:

Brainstorming

We place special emphasis on the dynamics of team work, and how these dynamics are applied to the successful use of CRC. The first team strategy we suggest is brainstorming. We show how this applies to the task of finding classes and listing scenarios.

Role Plays

The second team strategy we recommend is role play. CRC cards provide a uniquely dynamic way of testing out your conception of the system and evaluating potential paths of collaboration. Role plays get everyone involved and invested in the system.

Case Studies

Three case studies are provided to help you visualize how the guidelines developed in the descriptive chapters might be applied in a real-life situation. All three case studies are based on real systems. They are presented in a dramatic, novella style to demonstrate more clearly how personalities and organizational culture come into play when a group is using the CRC technique. This is especially important in the context of brainstorming and role play. We hope that this approach not only will clarify the use of the method, but will provide a little entertainment along the way!

Implementations in Code

We also provide two examples of how our third case study, the control of automobile traffic intersections, might look when a programmer uses CRC cards as the basis for coding in Smalltalk, C++, and JAVA. Three experts in each language community joined with us to write this unique material.

Managing Object Analysis

Following the examination of role playing in the CRC method, we discuss the overall demands of managing an object-oriented project, along with suggestions as to useful metrics for monitoring the process, and for including legacy software in OO systems. We also provide some ideas for the transition from informal modeling with CRC cards to the use of a full-blown, formal methodology such as Schlaer-Mellor or the Unified Modeling Language. The final case study in the book provides additional insight into the application of these techniques.

Transition to Methodologies

In this concluding chapter we discuss the limitations of CRC cards and examine several popular and more comprehensive object-oriented analysis and design methodologies.

CRC Roadmap

Every chapter is full of useful tips, tricks, and pointers drawn from the real world. In addition to the various tables and lists in the text, we've collected these together in an appendix with pointers back into the book, so you can find things quickly when you need them.

Get to Work!

In The CRC Card Book, we have tried to distill a wide range of experiences and training tips for the use of CRC. We hope that some of it applies to all of you, and that all of it applies to some of you. Above all, remember, let CRC make your team work fun!

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Table of Contents

About the Authors.


Figure List.


Foreword.


Preface.


Acknowledgments.


1. CRC: A Problem-Solving Technique.