No description available.

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No description available.

Thesis (Ph. D.)--Massachusetts Institute of Technology. / Vita. Includes bibliographical references (p. 281-284).

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves D-1-D-9).

There has been little published about the characteristics of computer jobs running on modern time-sharing computer systems, due largely to the lack of appropriate programs and equipment necessary to measure the parameters involved. In this thesis, measures are presented for some of the important characteristics of jobs. The Data Collection Facility, which is part of the Michigan Terminal System, was used to this end. The Michigan Terminal System is a time-sharing operating system for the IBM 360/67 computer, and supports batch and terminal users simultaneously. Chapter 1 gives an outline of the problem, and other work which has been done in this line. It also contains a reasonably detailed description of the Michigan Terminal System. In Chapter 2, measurements of requested CPU service, CPU service obtained, system and user response times, I/O delays, and page waiting times are given. Chapter 3 outlines the storage requirements of jobs, and gives a model which will generate profiles of storage required by jobs over their running times, which are very similar to profiles observed for actual jobs. Some discussion of the results is given in chapter 4, and also a simple model of the system is shown which might be used in a simulation study employing measurements taken in this study. / Science, Faculty of / Computer Science, Department of / Graduate

No description available.

Most computing systems are shared between users of various kinds. This thesis treats such systems as mathematical objects, and investigates two of their properties: refinement and security. The first is the analysis of the conditions under which one shared system can be replaced by another, the second the determination of a measure of the information flow through a shared system. Under the heading of refinement we show what it means for one shared system to be a suitable replacement for another, both in an environment of co-operating users and in an environment of independent users. Both refine- ment relations are investigated, and a large example is given to demonstrate the relation for cooperating users. We show how to represent the security of a shared system as an 'inference function', and define several security properties in terms of such functions. A partial order is defined on systems, with the meaning 'at least as secure as'. We generalise inference functions to produce 'security specifications' which can be used to capture the desired degree of security in any shared system. We define what it means for a shared system to meet a security specification and indicate how implementations may be derived from their specifications in some cases. A summary of related work is given.

Thesis--Massachusetts Institute of Technology. / Vita. Bibliography: p. 235-236.

Thesis (Ph. D.): Massachusetts Institute of Technology. / Includes bibliographical references (p. 186-187).