Identifying objects in legacy systems using design metrics

Abstract

Many organisations are migrating towards object-oriented technology. However, owing to the business value of legacy software, new object-oriented development has to be weighed against salvaging strategies. The incremental migration of procedurally oriented systems to object-oriented platforms seems to be a feasible approach, although it must be considered as risky as redevelopment. This approach uses reverse engineering activities to abstract an object-oriented model from legacy code. The paper presents a method for decomposing legacy systems into objects. The identification of objects is centred around persistent data stores, such as files or tables in the database, while programs and routines are candidates for implementing the object methods. Associating the methods to the objects is achieved by optimising selected object-oriented design metrics. The rationale behind this choice is that the object-oriented decomposition of a legacy system should not result in a poor design, as this would make the re-engineered system more difficult to maintain.