INTERACTIVE VISUAL DATA ABSTRACTION IN A DECLARATIVE VISUAL PROGRAMMING LANGUAGE

Visual data abstraction is the concept of data abstraction for visual languages. In this paper, 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, conceptual simplicity 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. 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 part of the programming process.