An Interactive Approach to Visual Data Abstration for Declarative Visual Programming Languages
Margaret Burnett, Allen L. Ambler · 1993
Visual data abstraction is the concept of data abstraction for visual languages. In this paper, the notion of visual data abstraction for declarative visual languages is explored. First, we discuss how the requirements of data abstraction for visual languages differ from the requirements for traditional textual languages. We then present a declarative approach to visual data abstraction in the language Forms/3. Within the context of this system, issues of particular importance to declarative visual languages are examined. These issues include enforcing information hiding through visual techniques, supporting abstraction while preserving concreteness and immediate feedback, conceptual simplicity, dealing with polymorphism, and specification of a type''s appearance and interactive behavior as part of its definition. Interactive behavior is seen to be part of the larger problem of event-handling in a declarative language. The approach to events supports system-level, interactive, and user-defined events, while still maintaining the property of referential transparency. A significant feature is that all programming and execution are done in a fully-integrated visual manner, without requiring other languages or tools for any partr of the programming process.