Formalizations in systems development

Formalizations are related both to types of expression and to types of behaviour. The limits to applying formalizations in these two senses are discussed and illustrated by examples from practical systems development. It will be established that formalizations are valuable in some situations, but insufficient in others. The alternative to uncritically using formalizations is that system developers analyse the situations in which they find themselves, and from there plan a combination of a formal and an informal approach.