From metaphors to microworlds. The challenge of creating educational software

Every time we use a computer we are working with metaphors. In some cases the metaphor is obvious, and in others not. This aspect of the computer is what makes it so useful. User interface metaphors like desktops, menus and windows can make computing appear more like the “real” activities in which we take part. In the realm of educational software, the task of programming boils down to the creation of a metaphorical microworld in which the user can interact with tasks and simulations that are designed to aid the acquisition and development of knowledge.Programming is hard no matter which language is used. The reasons why traditional authoring languages such as PILOT have failed to sweep through educational computing have nothing to do with the syntax or structure of programming languages but more to do with the failure of the underlying metaphor. The major difference between various high level languages are not to be found in their syntaxes, grammars, or vocabularies, but in their metaphors. A Pascal programmer sees a program as a collection of procedures, a Smalltalk programmer as objects and messages. The trick to making programming easy is to make the metaphor of the language match that of the application.Construction set languages including good spreadsheet programs have become immensely popular tools arising from their ease of use as a direct consequence of the consistency of the metaphor as one moves from programming to execution. Construction sets have a strong limitation; they are not general-purpose tools. The closest we have come to general purpose direct manipulation languages is with products like Filevision (a Macintosh-based visual database) and Guide.Paper-based media are very well suited to linear progression from one topic to another. As soon as it becomes important to branch between two activities, they become cumbersome to use. It is the ability of computer programs to branch which gives them quite different functions from documents. While programming languages allow the creation of branching programs, there is a new class of application programs which provide the same capability based on metaphors that are a natural evolution from the linear world of paper-based documents. Hypermedia is a term that refers to this class of software, not to one particular application; for example, Filevision is a hypermedia database tool. Hypermedia tools have great potential as authoring systems and they can make life much more exciting for those of us involved in educational computing.