Resource sharing across heterogenous networks

Sharing resources on a computer network, especially in heterogeneous environments, has m any benefits: new applications become possible, and use of technology cheaper. This dissertation investigates how resources— in particular printing resources—may b e shared. While still incomplete, an existing theoretical framework for data communication and resource sharing, the ISO-051 Reference Model, provides useful background information and tools for analysis. A discussion o f this framework complements a survey o f the principles and current state of file and printer servers, and distributed systems. An analysis of the design and implementation of a printer server acting as a b ridge between two networks illustrates problem s and results found in distributed system s generally. The dissertation concludes by analyzing the strengths and shortcomings of the Reference Model and distributed systems. This and developments in technology lead to a proposal of an extended model for printer services, and clarification of printer servers' needs and requirements

The slicing extent technique for fast ray tracing

A new technique for image generation using ray tracing is introduced. The “Slicing Extent Technique” (SET) partitions object space with slicing planes perpendicular to all three axes. Planes are divided into two dimensional rectangular cells, which contain pointers to nearby objects. Cell size and the space between slices varies, and is determined by the objects’ locations and orientations. Unlike oct-tree and other space-partitioning methods, SET is not primarily concerned with dividing space into mutually exclusive volume elements (‘voxels’) and identifying objects within each voxel. Instead, SET is based on analysis of projections of objects onto slicing planes. In comparison to the existing space subdivision methods for ray tracing, SET avoids tree traversal and exhibit no anomalous behavior. There is no reorganization when new objects arrive. Preprocessing to create slices is inexpensive and produces a finely tuned filter mechanism which supports rapid ray tracing

Surface interaction : separating direct manipulation interfaces from their applications.

To promote both quality and economy in the production of applications and their interactive interfaces, it is desirable to delay their mutual binding. The later the binding, the more separable the interface from its application. An ideally separated interface can factor tasks from a range of applications, can provide a level of independence from hardware I/O devices, and can be responsive to end-user requirements. Current interface systems base their separation on two different abstractions. In linguistic architectures, for example User Interface Management Systems in the Seeheim model, the dialogue or syntax of interaction is abstracted in a separate notation. In agent architectures like Toolkits, interactive devices, at various levels of complexity, are abstracted into a class or call hierarchy. This Thesis identifies an essential feature of the popular notion of direct manipulation: directness requires that the same object be used both for output and input. In practice this compromises the separation of both dialogue and devices. In addition, dialogue cannot usefully be abstracted from its application functionality, while device abstraction reduces the designer's expressive control by binding presentation style to application semantics. This Thesis proposes an alternative separation, based on the abstraction of the medium of interaction, together with a dedicated user agent which allows direct manipulation of the medium. This interactive medium is called the surface. The Thesis proposes two new models for the surface, the first of which has been implemented as Presenter, the second of which is an ideal design permitting document quality interfaces. The major contribution of the Thesis is a precise specification of an architecture (UMA), whereby a separated surface can preserve directness without binding in application semantics, and at the same time an application can express its semantics on the surface without needing to manage all the details of interaction. Thus UMA partitions interaction into Surface Interaction, and deep interaction. Surface Interaction factors a large portion of the task of maintaining a highly manipulable interface, and brings the roles of user and application designer closer

Structured Graphics for Distributed Systems

includes bibliography: pp. 48-51. One of the most important functions of an intelligent workstation is to provide a state-of-the-art user interface to distributed resources. One aspect of such an interface is virtual terminal support for both local and remote applications with a range of requirements, including graphics. To ensure good response for remote applications in particular, the bulk of user interaction must be handled local to the workstation. Therefore, the terminal management software on the workstation must provide object modelling as well as viewing facilities, in contrast to most contemporary graphics systems. One way of doing this is to support structured display files. It is equally important to support simultaneous access to multiple applications, thus the terminal management software must provide window system facilities. Lastly, since the terminal management software should present a common interface to both local and remote applications, the workstation itself should be regarded as a multifunction component of the distributed system and not strictly as a terminal or a personal computer. This paper presents the system architecture and protocols necessary to achieve these goals and evaluates an existing implementatio