SUMMARY Object-oriented design translates the OOA model of the real world into an

22.6 SUMMARY Object-oriented design translates the OOA model of the real world into an

implementation-specific model that can be realized in software. The OOD process can be described as a pyramid composed of four layers. The foundation layer focuses on the design of subsystems that implement major system functions. The class layer specifies the overall object architecture and the hierarchy of classes required to imple- ment a system. The message layer indicates how collaboration between objects will

be realized, and the responsibilities layer identifies the attributes and operations that characterize each class. Like OOA, there are many different OOD methods. UML is an attempt to provide

a single approach to OOD that is applicable in all application domains. UML and other methods approach the design process through two levels of abstraction—design of subsystems (architecture) and design of individual objects.

During system design, the architecture of the object-oriented system is devel- oped. In addition to developing subsystems, their interactions, and their place- ment in architectural layers, system design considers the user interaction component, a task management component, and a data management compo- nent. These subsystem components provide a design infrastructure that enables the application to operate effectively. The object design process focuses on the description of data structures that implement class attributes, algorithms that implement operations, and messages that enable collaborations and object rela- tionships.

Design patterns allow the designer to create the system architecture by integrat- ing reusable components. Object-oriented programming extends the design model into the executable domain. An OO programming language is used to translate the classes, attributes, operations, and messages into a form that can be executed by a machine.

CHAPTER 22 OBJECT-ORIENTED DESIGN

REFERENCES [BEN99] Bennett, S., S. McRobb, and R. Farmer, Object Oriented System Analysis and

Design Using UML, McGraw-Hill, 1999. [BIH92] Bihari, T. and P. Gopinath, “Object-Oriented Real-Time Systems: Concepts and Examples,” Computer, vol. 25, no. 12, December 1992, pp. 25–32. [BOO94] Booch, G., Object-Oriented Analysis and Design, 2nd ed., Benjamin Cum- mings, 1994. [BOO99] Booch, G., I. Jacobson, J. Rumbaugh, The Unified Modeling Language User Guide, Addison-Wesley, 1999. [BRO91] Brown, A.W., Object-Oriented Databases, McGraw-Hill, 1991. [BUS96] Buschmann, F., et al., A System of Patterns: Pattern Oriented System Archi- tecture, Wiley, 1996. [CHA93] De Champeaux, D., D. Lea, and P. Faure, Object-Oriented System Develop- ment, Addison-Wesley, 1993. [COA91] Coad, P. and E. Yourdon, Object-Oriented Design, Prentice-Hall, 1991. [COX85] Cox, B., "Software ICs and Objective-C," UnixWorld, Spring 1985. [DAV95] Davis, A., “Object-Oriented Requirements to Object-Oriented Design: An Easy Transition?” Journal of Systems Software, vol. 30, 1995, pp. 151–159. [DOU99] Douglass, B., Real-Time UML: Developing Efficient Objects for Embedded Sys- tems, Addison-Wesley, 1999. [FIC92] Fichman, R. and C. Kemerer, "Object-Oriented and Conceptual Design Methodologies," Computer, vol. 25, no. 10, October 1992, pp. 22–39. [GAM95] Gamma, E., et al., Design Patterns, Addison-Wesley, 1995. [GOL83] Goldberg, A. and D. Robson, Smalltalk-80: The Language and Its Implemen- tation, Addison-Wesley, 1983. [JAC92] Jacobson, I., Object-Oriented Software Engineering, Addison-Wesley, 1992. [JAC99] Jacobson, I., G. Booch, J. Rumbaugh, Unified Software Development Process, Addison-Wesley, 1999. [MEY90] Meyer, B., Object-Oriented Software Construction, 2nd ed., Prentice-Hall, 1988. [PRE95] Pree, W., Design Patterns for Object-Oriented Software Development, Addison- Wesley, 1995. [RUM91] Rumbaugh, J., et al., Object-Oriented Modeling and Design, Prentice-Hall, 1991. [RUM99] Rumbaugh, J., I. Jacobson, and G. Booch, The Unified Modeling Language Reference Manual, Addison-Wesley, 1999. [RAO94] Rao, B.A., Object-Oriented Databases: Technology, Applications and Products, McGraw-Hill, 1994. [TAY92} Taylor, D.A., Object-Oriented Information Systems, Wiley, 1992. [WIR90] Wirfs-Brock, R., B. Wilkerson, and L. Weiner, Designing Object-Oriented Soft- ware, Prentice-Hall, 1990.

627