A model, architecture, and operating system support for shared workspace cooperation
Sheng-Uei Guan, Hussein M. Abdel-Wahab · 1989
As more and more special-purpose real-time user cooperation tools are being built, the impact of these new applications to operating systems has just emerged. Instead of directly implementing an operating system for such applications, we try to identify user requirements for such cooperation and the support that designers of such tools seek. With this investigation, the desirable requirements and support can then be achieved through different approaches, e.g. operating system kernels, on-line libraries, or user module libraries. Rather than tackle the problem in its full generality, we focus on real-time cooperation with shared workspaces, which is the core of most real-time cooperation. This dissertation describes a shared workspace model. Subtleties supporting this shared workspace have been studied. A Remote Shared Workspaces facility has been built as a research vehicle. Desirable features for shared workspace cooperation are investigated; the relevance of operating systems supporting them is also discussed. An architecture supporting dynamic groups formation and activities is presented. It supports remote cooperation and also cooperation with existing single-user applications. Operating system mechanisms are also described to support multi-user tools development and sharing of user privileges in a session, namely: multi-user processes and shared capabilities-lists. A system-call level programmers' interface has been specified. We also introduce objects, found in real life and the computer world. The use of multi-user tools makes the existence of objects a necessity: a participant who joins a multi-user tool written by others knows that the user agent executed in his name is not a Trojan horse if the multi-user tool is jointly owned by all the participants. The concept of jointly-owned is generalized to jointly-owned, which helps resolve conflicts among joint owners. Graham and Denning's protection model is extended to incorporate these conditionally entities. Authority- and quorum-based objects are investigated as instances of conditionally objects.