Abstract. SELF is an object-oriented language for exploratory programming based on a small number of simple and concrete ideas: prototypes, slots, and behavior. Prototypes combine inheritance and instantiation to provide a framework that is simpler and more flexible than most object-oriented languages. Slots unite variables and procedures into a single construct. This permits the inheritance hierarchy to take over the function of lexical scoping in conventional languages. Finally, because SELF does not distinguish state from behavior, it narrows the gaps between ordinary objects, procedures, and closures. SELF’s simplicity and expressiveness offer new insights into objectoriented computation. To thine own self be true. —William Shakespeare 1

Abstract not found

user interface management system (UIMS). We describe Pad++, a zoomable graphical sketchpad that we are exploring as an alternative to traditional window and icon-based interfaces. We discuss the motivation for Pad++, describe the implementation, and present prototype applications. In addition, we introduce an informational physics strategy for interface design and briefly contrast it with current design strategies. We envision a rich world of dynamic persistent informational entities that operate according to multiple physics specifically designed to provide cognitively facile access and serve as the basis for design of new computationally-based work materials. 1 To appear in the Journal of Visual Languages and Computing.

Unidraw is a framework for creating graphical editors in domains such as technical and artistic drawing, music composition, and circuit design. The Unidraw architecture simplifies the construction of these editors by providing programming abstractions that are common across domains. Unidraw defines four basic abstractions: comporzents encapsulate the appearance and behavior of objects, tools support direct manipulation of components, commands define operations on components, and external representations define the mapping between components and the file format generated by the editor. Unidraw also supports multiple views, graphical connectivity, and dataflow between components. This paper describes the Unidraw design, implementation issues, and three experimental domain-specific editors we have developed with Unidraw: a drawing editor, a user interface builder, and a schematic capture system. Our results indicate a substantial reduction in implementation time and effort compared with existing tools.

Finding the configurations of a set of rigid bodies that satisfy a set of geometric constraints is a problem traditionally solved by reformulating the geometry and constraints as algebraic equations which are solved symbolically or numerically. But many such problems can be solved by reasoning symbolically about the geometric bodies themselves using a new technique called degrees of freedom analysis. In this approach, a sequence of actions is devised to satisfy each constraint incrementally, thus monotonically decreasing the system's remaining degrees of freedom. This sequence of actions is used metaphorically to solve, in a maximally decoupled form, the equations resulting from an algebraic representation of the problem. Degrees of freedom analysis has significant computational advantages over conventional algebraic approaches. The utility of the technique is demonstrated with a program that assembles and kinematically simulates mechanical linkages. Introduction Solving geometric con...

Many graphics tasks, such as the manipulation of graphical objects, and the construction of userinterface widgets, can be facilitated by geometric constraints. However, the difficulty of specifying constraints by traditional methods forms a barrier to their widespread use. In order to make constraints easier to declare, we have developed a method of specifying constraints implicitly, through multiple examples. Snapshots are taken of an initial scene configuration, and one or more additional snapshots are taken after the scene has been edited into other valid configurations. The constraints that are satisfied in all the snapshots are then applied to the scene objects. We discuss an efficient algorithm for inferring constraints from multiple snapshots. The algorithm has been incorporated into the Chimera editor, and several examples of its use are discussed. 1 Introduction Geometric constraints are used extensively in computer graphics in the specification of relationships between graph...

We have implemented a comprehensive constraintbased programming language as an extension to Common Lisp. This constraint package provides a unified framework for solving both numeric and non-numeric systems of constraints using a combination of local propagation techniques including binding propagation, Boolean constraint propagation, generalized forward checking, propagation of bounds, and unification. The backtracking facility of the nondeterministic dialect of Common Lisp used to implement this constraint package acts as a general fallback constraint solving method mitigating the incompleteness of local propagation. Introduction Recent years have seen significant interest in constraint logic programming languages. Numerous implementations of such languages have been described in the literature, notably clp(!) (Jaffar and Lassez 1987) and CHiP (Van Hentenryck 1989). The point of departure leading to these systems is the observation that the unification operation at the core of lo...

Abstract not found

People benefit from tightly integrated systems that can be designed, realized and evolved affordably. Unfortunately, common software design methods do not easily accommodate requirements for tightly integrated systems. Indeed, when used to meet such requirements, common methods tend to yield unnecessarily complex structures that complicate design and realization and that inhibit subsequent evolution. After substantiating this claim, I present the mediator method as a solution. This method combines behavioral entity-relationship (ER) modeling for design with a mediator approach to implementation. The mediator method is better than common methods for designing, realizing, and evolving many integrated systems. I support this claim both by rational argument from simplifying models and by careful...

Layout refers to the process of determining the sizes and positions of the visual objects that are part of an information presentation. Automated layout refers to the use of a computer program to automate either all or part of the layout process. This field of research lies at the crossroads between artificial intelligence and human computer interaction. Automated layout of presentations is becoming increasingly important as the amount of data that we need to present rapidly overtakes our ability to present it manually. We survey and analyze the techniques used by research systems that have automated layout components and suggest possible areas of future work.