1 Issues in Object - Oriented Language Design

My guess is that object-oriented programming will be in the 1980s what structured programming was in the 1970s. Everyone will be in favor of it. Every manufacturer will promote his products as supporting it. Every manager will pay lip service to it. Every programmer will practice it (differently). And no one will know just what it is. Tim Rentsch in [Ren82] In this chapter we explore essential aspects of object-oriented programming languages in a top-down approach. Section 1.1 gives a view of object-oriented programming from the perspective of knowledge representation and argues that object-oriented programming supports a number of important abstraction principles. Section 1.2 covers aspects of software development. Here the notions of late binding, inheritance and encapsulation play a central role. Section 1.3 introduces central issues of concurrent programming as relevant to object-oriented programming. Software is used to solve problems in given domains. To this aim, software expresses properties of entities, their relationship and interaction in a language accessible to automatic treatment such as compilation to processor instructions. The complexity of a given domain of application must be matched by the expressivity of the language in use. To understand a complex problem it is necessary to view it from different angles provided by abstraction principles. An often quoted hallmark of object-oriented programming is its support for the knowledge representation principles of classification, aggregation and specialization [Tai96].