Using Algebraic Constraints in Interactive Text and Graphics Editing

Abstract

In many graphical application areas such as architectural and mechanical design, spatial relationships are vastly used to construct and manipulate complex objects. They are used to describe dependencies between components in objects or between objects and their contexts. These relationships, especially the precise ones, can be represented with algebraic relations and appropriately processed by using constraint programming techniques. Rather than embedding relationships in pre-defined objects, this approach offers possibility to treat relationships explicitly. This paper presents an editing program for presentation materials. The program provides facilities to interactively specify and modify relationships such as alignment, connection and enclosure. The normal editing operations are combined with constraint satisfaction so that an operation on one object may also change the related objects in a chain reaction fashion. A constraint satisfaction algorithm has been implemented in the program. This algorithm is able to solve linear equations.