Pattern Metrics in OOAD

Object-Oriented Analysis and Design (OOAD) has at last come of age; it is the preferred software development technology today. Sophisticated online transaction-oriented applications and systems in aerospace and medical technology have been using C++ for years. The emergence of Java as the preferred language for Internet application development has established OOAD and Object-Oriented Programming (OOP) as major players. Many college and university computer science programs are Java-based nowadays, and many application groups are busy converting COBOL and PL/1 applications to Java. The use of OOAD both in the development of new systems and in their conversion from legacy procedural language implementations favors the discovery and use of design patterns. A design pattern is a microarchitecture that provides a proven solution to design problems that tend to recur within a given application or software development context. A design pattern includes its static structure as the hierarchy of classes and objects in the pattern and their relationships. It also includes the behaviors (to use the Java term) or dynamic relationships that govern how the objects exchange messages. Design patterns are classified by their users into three groups; they are either creational, structural, or behavioral. Creational patterns concern object creation. Structural patterns capture class or object composition. Behavioral patterns deal with how classes and objects interact. Most patterns are discovered in existing software packages when they are either modified or rewritten by very senior programmers or software architects who notice their repetitive occurrences. A research group at the Institute for Scientific and Technical Research in Trento, Italy has developed a set of metrics for OO software applications that allow them to extract design patterns automatically.^[21]

Ostensibly the major benefit of understanding and using repeating design patterns in OOP is to enhance code reusability. However, software quality enhancement has significant benefits as well. Not only do patterns reduce the unique SLOC in an application, they also reduce its effective volume, increase development productivity, and simplify later enhancement and maintenance. The technology frontier in software development today is learning how to break high-level architectural design into its architectural components. This is similar to how a building architect breaks his or her overall design into horizontal microarchitectures such as stories and plazas and into vertical micro-architectures or infrastructure components such as HVAC, plumbing, power, elevators, and stairways.

The future of software quality is further automation by automatic program generation. This means the ability to break the overall customer-responsive architecture (form follows function) into successively lower levels of architecture, down to micro-architectures such as design patterns from which quality application software can be generated automatically.