Understanding Symmetry in Object-Oriented Languages

The success of symmetry applications in many scientific disciplines has motivated us to explore symmetry in software. Our exploration is based on an informal notion that symmetry is the possibility of making a change together with some aspect that is immune to this change. In this view, symmetry has a duality of change and constancy whereby some aspect of an object can be changed while leaving other key aspects invariant. This view of symmetry is a fundamental concept underpinning many symmetry principles in the physical sciences. We have found that we can explain some object-oriented language constructs using this notion of symmetry. This article explores symmetry in object-oriented languages and also provides other examples of symmetry outside of object-oriented programming to show that symmetry considerations broaden beyond object orientation to other areas of software design.