Software engineers produce many descriptions: those of the environment or domain in which a desired computing system software is to exist; descriptions of the requirements put on the software; and descriptions of the software design that implements the requirements. Thus the descriptions span the spectrum from application domain, via requirements and software architecture, program organisation and lower level designs, to executable code. While its concerns may be general, software engineering is unique among engineering disciplines in that its primary products are descriptions that must eventually satisfy the laws of mathematical logic and metamathematics.

Other engineering disciplines have to handle a quantum leap into physical reality – the stuff of natural science. In software engineering there is a different quantum leap: that from description to execution. Software engineering is thus about structuring and relating descriptions.

Abstraction and modelling taken together are the keys to mastering the complexity of environments and systems. Formal specification is employed to express abstractions and to ensure affinity to real domains. Such specifications open up ways to establish the proper relation between domain and requirements models as well as potentially verifying the links between software architecture, requirements models and the stages of design. This increases the chance of achieving a proper fit to the environment, to user expectations and of the correctness of implementation.