The Juno-2 Constraint-Based Drawing Editor

Allan Heydon, DEC Research Center

Seminar on People, Computers, and Design
Stanford University May 12, 1995

(Joint work with Greg Nelson)


Constraints are an important enabling technology for interactive graphics applications. However, today's constraint-based systems are plagued by several limitations, and constraints have yet to live up to their potential.

Juno-2 is a constraint-based double-view drawing editor that addresses some of these limitations. Constraints allow you to specify locations in your drawing declaratively. The constraints are maintained whenever part of the picture is changed, so constraints make it easier to maintain a picture in the face of modifications. Some constraints are pre-defined by the Juno-2 application, but the program also includes a powerful extension language that allows users to define new constraints. The system demonstrates that fast constraint solving is possible with a highly extensible, fully declarative constraint language.

The talk will include a videotape demonstration of Juno-2, including some of our recent experiments using it to model constrained three- dimensional shapes, and to produce animations.


Allan Heydon works at Digital Equipment Corporation's Systems Research Center in Palo Alto, CA. He is a co-developer of Juno-2, a constraint-based drawing editor. More recently, he has been working on the Vesta software configuration management system. His general research interests include formal methods, visual specification languages, programming development environments, and user interfaces. He received his PhD in computer science from Carnegie Mellon University in 1991, where he designed and implemented a system for processing visual specifications of file system security.


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