Alterable visual languages

The large number of programming languages in the world is, in part, a consequence of the broad spectrum of human preferences for different notational styles and semantic models, which seems to depend on personal background as well as the application area involved. A move from text to visual languages seems to increase variety, because of the greater syntactic flexibility allowed; a single person might choose a variety of syntax conventions for different application areas. This has led to an increasing focus on language frameworks, structures within which families of languages can be embedded, such that components written in different languages can still be linked together for use. An operational approach to designing a framework is to examine what languages have in common, and what can be allowed to vary: that is, defining operations that allow for the direct manipulation of languages as first class objects