A constraint describes a relation to be maintained

The SkyBlue constraint solver is an efficient incremental algorithm that uses local propagation to maintain sets of required and preferential constraints. SkyBlue is a successor to the DeltaBlue algorithm, which was used as the constraint solver in the ThingLab II user interface development environment. Like DeltaBlue, SkyBlue represents constraints between variables by sets of short procedures (methods) and incrementally resatisfies the set of constraints as individual constraints are added and removed. DeltaBlue has two significant limitations: cycles of constraints are prohibited, and constraint methods can only have a single output variable. SkyBlue relaxes these restrictions, allowing cycles of constraints to be constructed (although SkyBlue may not be able to satisfy all of the constraints in a cycle) and supporting multi-output methods. This paper presents the SkyBlue algorithm and discusses several applications that have been built using SkyBlue. 1 Introduction The DeltaBlue a...

We propose a reflective model to express and to automatically manage dependencies between objects. This model describes reflective facilities which enable the changing of language semantics. Although the importance of inter-object dependencies is well accepted, there is only limited object-oriented language support for their specification and implementation. In response to this lack of expressiveness of object models, the flo language integrates dependency management into the object oriented paradigm. Dependencies are described as first class objects and flo automatically maintains the consistency of the dependency graph.

Constraints provide a useful mechanism for maintaining relations in user interface toolkits. Garnet is a widely-used user interface toolkit with considerable functionality, based on one-way, required constraints. Multi-Garnet extends Garnet by adding support for multi-way constraints and constraint hierarchies with both required and preferential constraints. This document contains three chapters describing Multi-Garnet: ffl Chapter 1 presents a high-level overview of Multi-Garnet. To motivate the development of Multi-Garnet, we examine the Garnet constraint system, present some realistic user interface problems that are difficult to handle in Garnet, and demonstrate how Multi-Garnet addresses these problems. We provide details on how Multi-Garnet supports some of the features of Garnet, including constraints with pointer variables, and inheritance of constraints. ffl Chapter 2 contains a reference manual for the current version of Multi-Garnet (version 2.1). This includes information ...

This paper describes the VB2 architecture for the construction of three-dimensional interactive applications. The system's state and behavior are uniformly represented as a network of interrelated objects. Dynamic components are modeled by active variables, while multi-way relations are modeled by hierarchical constraints. Daemons are used to sequence between system states in reaction to changes in variable values The constraint network is efficiently maintained by an incremental constraint solver based on an enhancement of SkyBlue. Multiple devices are used to interact with the synthetic world through the use of various interaction paradigms, including immersive environments with visual and audio feedback. Interaction techniques range from direct manipulation, to gestural input and threedimensional virtual tools. Adaptive pattern recognition is used to increase input device expressiveness by enhancing sensor data with classification information. Virtual tools, which are encapsulations...

Multimedia data has become readily available from a variety of resources, such as the Web, to users (ranging from naive to sophisticated) who need to select and to present the data in a way that is meaningful to their particular applications. Delaunay MM is our framework for querying and presenting multimedia data stored in distributed data repositories, including the Web. It is unique in combining user-defined layouts with ad hoc querying capabilities, thereby enabling users to tailor, in a simple way, the layout of virtual documents composed of retrieved multimedia objects. In this paper, we focus on the object-oriented data models, on the declarative query languages, and on how the results of the queries to disparate resources are integrated to form coherent user-defined documents. 1 Introduction Database management systems (DBMSs) have traditionally enabled the storage, retrieval, and presentation of tabular datasets primarily for professional applications. The recent phenomenon...

We present Pika, an implemented self-explanatory simulator that is more than 5000 times faster than SimGen Mk2 [ Forbus and Falkenhainer, 1992 ] , the previous state of the art. Like SimGen, Pika automatically prepares and runs a numeric simulation of a physical device specified as a particular instantiation of a general domain theory, and it is capable of explaining its reasoning and the simulated behavior. Unlike SimGen, Pika's modeling language allows arbitrary algebraic and differential equations with no prespecified causal direction; Pika infers the appropriate causality and solves the equations as necessary to prepare for numeric integration. Introduction Science and engineering have used numeric simulation productively for years. Simulation programs, however, have been laboriously hand-crafted, intricate, and difficult to understand and change. There has been much recent work on automating their construction (e.g. [ Yang, 1992, Rosenberg and Karnopp, 1983, Abelson...

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. Constraint Imperative Programming (CIP) languages integrate declarative constraints with imperative state and destructive assignment, yielding a powerful new programming paradigm. However, CIP languages are difficult to implement efficiently due to complex interactions between the two donor paradigms. Neither the virtual machines for classical object-oriented languages, nor those for existing constraint languages, are suitable for implementing CIP languages, as each assumes a purely imperative or a purely declarative computation model. We have developed a new virtual machine for CIP languages, the K-machine, an imperative machine with an incremental constraint solver and a constraint-based, rather than value-based, data store. This virtual machine allows user-defined constraints to be defined using constraint constructor definitions which are the CIP analog to method definitions. Similar to methods, these constructors are able to reference variables indirectly through many levels of ...

Constraint imperative programming is an integration of declarative constraints and imperative object-oriented programming. The primary goal of this integration is to use constraints to express relations among objects explicitly--- relations that were implicit in the code in previous languages. However, one of the fundamental concepts of object-oriented programming, object identity, can result in implicit relations, even when explicit identity constraints are supported. We analyze the problem and propose a solution ---identity constraints---which we have implemented in our Kaleidoscope'93 language. This solution is understandable, efficiently implementable, and compatible with the Kaleidoscope constraint model.