Jointly-owned objects for collaboration: Operating-system support and protection model

As real-time collaboration becomes more frequent, it is common for a group of users to create and own an object jointly. The use of multi-user tools makes the existence of jointly owned objects a necessity: a participant who joins a multi-uscr 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. In this paper, we discuss the requirements and issues behind jointly-owned objects. By generalizing these requirements we have implemented a conditionally jointly-owned object. The conditions take the form of a quorum or a list of users who have the rights to access an object or to change its protection state. We sketch a design of conditionally jointly-owned objects, and apply the same concepts to subjects. Authority- and quorum-based objects are investigated as instances of conditionally joinly-owncd objects. We show that conditionally jointly-owned objects can also be used to resolve the conflicts that may arise among joint owners. We generalize Graham and Denning's protection model to incorporate these jointly-owned entities. Operating system support for conditionally jointly-owned objects is specified at the system-call level. Examples are provided to demonsuate the usefulness of conditionally jointly-owned objects

Program Translation Fundamentals: Methods And Issues

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Pc-Dos Fundamentals For Diskette-Based Operation

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Assemblers, Compilers, And Program Translation

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ABSTRACT Slotted Priorities: Supporting Real-Time Computing Within General-Purpose Operating Systems

Recent advances in network technologies, processor capabilities, and micro-computer system hardware, coupled with the explosive growth of the Internet and on-line data access, have created new demands on personal computer operating systems and hardware. In large part, these demands are for the ability to acquire, manipulate, display, and store multimedia data. The computational processes that successfully acquire and display multimedia data necessarily have deadlines. That is, the computation must be complete before a speci ed point in time. Currently, no general-purpose operating systems support such real-time processes. We have developed a software architecture, called slotted priorities, that de nes a way to add support for real-time computation to existing general-purpose operating sys-tems for uniprocessor machine architectures. The slotted priorities architecture shares the resources of a computing system between a general-purpose operating system and a real-time kernel. Software components called executives manage how an instance of a resource is shared. Executives ensure that the RTK can gain ac-cess to the resource at precise times. The resulting operating system will be abl