A Notation for the Visual Specification of Geometric Relations in Rule-based User Interface Development Environments

This paper describes a new visual notation for specifying geometric relationships (for example, in a user interface presentation application). This notation is designed to provide a centerpiece for the visual specification of predicates and rules in the BluePrint rule-based user interface development environment. The notation, while simple and using only a handful of operator symbols, is extremely powerful and expressive. It operates in an intuitive fashion using analogies to the physically based concepts of alignment and measurement to express a wide range of linear relationships between presentation objects, and can be used to express dynamic as well as static properties.