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This paper describes and compares the application of two alternative approaches to the identification of linear systems from input-output data. The first approach is based on fitting input and output data by sums of exponentials and deriving both the system structure and the parameter values from the resulting functions. The second approach is based on assuming a differential-equation structure and finding only the parameter values from the given data. The relative advantages, disadvantages, and computational aspects of both approaches are discussed with reference to a specific biological problem. The results are applicable to a variety of engineering and scientific problems described by systems of first-order linear differential equations.

This paper describes the SIMSCRIPT systems simulation language and the philosophy of system structure on which it is based. Application of the language to programming both discrete and continuous models is indicated and illustrated with examples. SIMSCRIPT processing is described and statistics regarding operating characteristics are given. The SIMSCRIPT system was developed at The RAND Corporation1,4 by a group including the second author.

Application of error correcting coding is often employed to improve system operation and reliability. By means of suitable reliability models and simple analysis, the effect of error correcting coding of memory words on the overall reliability of the system is discussed. Introduction of error correcting facilities will generally have three significant effects on the system: 1) increased hardware, which is also subject to failures and hence tends to lower reliability; 2) the system's ability to function in the presence of a certain class of failures; and 3) quicker detection of errors, which also means an improved repair rate. To illustrate the extent to which the above three factors govern the reliability improvement due to coding, three types of systems are considered. These systems use the same basic processor and memory units but differ in their structure and complexity. Other factors besides the three above which control the reliability improvement due to coding are the system structure and the relative sizes of processor and memory hardware.

A large scale system structure is considered for the case where the performance functional is not a simple sum of local performance indices. A decomposition method of the large scale problem consists of modifying the local performance functionals according to the global performance requirements. The large scale problem and its decomposition are formulated in Hilbert space; a formulation as a control problem is also presented as an example of possible detailed formulations. The properties of the decomposed problem are investigated. A new method of coordination based on an alternative approach to the variable operator method in Hilbert space is described; the basic properties of the method are analysed. A special feature of the variable operator method is stressed, which makes it possible to apply the method to large scale problems. The variable operator method is also useful in evaluating the sensitivity of the large scale structure to the coordination variables. A general discussion of sensitivity properties of large scale systems is also included. The large scale system structure and the method of evaluating its sensitivity can be of particular interest when applied to environmental control.

One of the least studied aspects of information retrieval is the relationship, on the linguistic plane, between the language of enquirers and the terms used by indexing systems. Much of the writing about system structure assumes that these are equivalent, that every enquirer is honest enough to call a spade a spade, and that the problems of designing descriptor languages for use in indexing he in the field of definition. This partly accounts for the sudden leap to fame of the thesaurus; for while a dictionary merely gives definitions of words one by one, a thesaurus, being slightly more refined, gives descriptive analyses in terms of synonyms and near‐synonyms, sometimes grouping them into sets based on some common characteristics.

A general synthesis problem is defined as that of determining an optimal system structure by extracting it from an enlarged system structure generated by splitting streams into alternative routes. When the optimized splitting ratio is close to 0 or 1, one of the alternative streams can be eliminated to give the optimal synthesis. Box's Complex method, is used to solve an actual example amenable to the integrated approach.

This paper presents a study of the effects of parameter variations on optimal process system structures and designs for biological wastewater treatment systems. Results indicate that optimal system structure and design are sensitive to variations in the rate constants and feed concentration. Some of the process flowsheets deduced are innovative and have surprisingly low total costs. The process system structures and designs developed in this study merit consideration in future planning and design of wastewater treatment systems.

In Part I of this article equations have been developed describing the behaviour of general deterministic systems. These lines of thought are followed up below, and are especially applied to systems the elements of which exhibit linear behaviour. By applying Laplace transform theory, it is established that matrix products determining the system behaviour, the operations of which were to be interpreted symbolically in Part I, are no longer symbolic. It is also shown how a future system behaviour may be obtained as the convolution of vectors, depending on initial values, and a system weight function matrix, depending entirely on structural properties of the system and on element behaviour.

The reliability at time t of a system in sustained operation is often taken to be the probability that it functions continuously during the time interval [0, t]. The standard computation of system reliability finds the probability that the system functions at time t in terms of the probabilities that its components function at time t. This procedure is relevant only if the system, and its components, have lives (roughly speaking, a device has a life if it functions continuously until some time of failure, and remains failed thereafter). We show that if each component of a coherent system has a life, then the system has a life (again roughly, a system is coherent if its performance is not impaired by an improvement in the performance of its components). Our principal results are that, under reasonable conditions, converses are true. If a system has a life, only a very weak condition is needed to show that the system is coherent. With a somewhat stronger condition, we show that not only must the system be c...

Assuming that the value of a scientific discipline depends upon the metapropositions upon which it is erected, the question is raised as to the logic of scientific psychology. Prevailing psychological foundations do not appear to meet natural science criteria. It is suggested that Interbehavioral Postulates offer satisfactory Propositions for a scientific psychology.

The data structure for a thesaurus is conceptually presented as a continuous string of characters. Hashing into the string permits access to terms and their related terms. A prefix hashing scheme is described which permits thesaurus access with partial spellings and defines file blocking to improve sequential (alphabetic) scans. A general system structure is proposed with display formats and a user command language.

A reliability model for multicomponent multistate systems is presented. This is a generalization of a model previously studied by Hirsch, Meisner, and Boll. In the earlier model, when a failure occurs for which no replacement spare is available, the locations using the same type of part as that having failed are “cannibalized” so as to allocate the shortages to locations where they are least detrimental to system performance. Here, we permit certain restrictions to be imposed upon the cannibalization procedure, and develop effective techniques for relating the probability laws governing the level of system performance to the system structure, cannibalization policy, kit of spare parts, and part reliabilities.

System size is an important variable in large, intricately structured systems. Such systems offer a greater scope of effect to size than do simpler types. Considering the potential usefulness of complex abstract systems as models of real-world systems, it becomes important 1) to determine the effect of size on behaviors of such systems, and 2) to seek procedures that indicate the effects of size indirectly. These two inquiries are undertaken in this paper for a basic class of complex system. An insensitivity of behavioral rhythm to change in system size, and a conjecture relating system size to system structure are examined.

Proper rearrangement of equality constraint equations can simplify considerably an otherwise complex optimization problem. This note shows that, with proper rearrangement, the equations describing a moderately complex chemical process can be solved seriatim. With such a system structure, the optimization procedure presented by Luus and Jaakola [A. I. Ch. E. J. 19, 760 (1973)] can be applied readily.

There is a need for systematic and well-thought-out high level language facilities or aids for enhancing the performance and cost/effectiveness of data management systems. Methodologies, practical models and associated software aids for data management system administration are much needed. The ideal goal is of course an automatic system administrator, a software black box, capable of choosing, generating and maintaining the best data management system structure, access paths and storage structure mappings for the particular data base, transaction traffic and computing and device characteristics. While this may not be practically achievable in the foreseeable future, due to the elusive multitude of parameters, trade-offs, interrelationships, etc., this should certainly be a goal.

A synopsis of computer system structure is presented. It is suggested that the current user interfaces should not be regarded as ends in themselves, but as steps towards more intelligent interaction with machines. The importance of understanding the present levels of engineering is stressed: the potential impact of new technologies such as "computer on a chip" or "microprogramming" can best be judged by reference to the well established framework of design.

The demands for flawless operation on the part of discrete systems often cannot be satisfied merely by high reliability of their constituent elements and the instigation of measures to assure infallibility of the systems themselves; in their design, therefore, it is necessary to adopt measures in order to guarantee so-called functional “stability,” or temporal reliability, through proper synthesis of the system structure, i.e., through a special choice of the number of elements in the system and of the character of their interconnections. Unstable operation of a discrete system can occur either due to the presence of random interference or due to interference brought on by a scatter of values of the time parameters† of the system elements. Whereas the influence of random interference or noise can be abated by proper filters or the assurance of d-reliability of the system, the elimination of interference caused by scatter of the time parameters of the elements can be taken care of in the appropriate stages of synthesis of the system by the introduction of structural redundancy, except that the introduction of structural redundancy in this instance differs from the introduction of structural redundancy for the assurance of d-reliability of the system.

A conceptual model is proposed for the use in the application of human engineering principles and techniques to the design of instructional systems. The trainee and instructor are viewed as operators within an information system. To illustrate this model and its application, examples are drawn from the literature and from current research on instructional systems. A preliminary human engineering guide is outlined which presents factors critical to design decisions for instructional systems. The model and guide attempt to counteract current tendencies toward premature standardization of instructional system structure, and to bring instructional system development into the main stream of the applied science of human engineering.

Introduction: On November 14, 1961, an environmental test program commenced on the first SNAP 10A system structure, S10A-PSM-1.

Following a request to all Commissions by the Executive Committee, a set of by-laws was prepared by the Organizing Committee and adopted by the Commission.

A model of the planning and programming aspects of a PPB system is formulated. It incorporates the component parts of a PPB system structure and the multiplicity of benefit and cost measures, both commensurable and incommensurable, so associated. Decision rules characterizing the choice of an efficient program package are derived. These rules indicate the usefulness of a program package numeraire. The comparative statics technique is applied and efficiency substitution and benefit effects derived. A program package cost- benefit function is developed. For a given program package decision, the expansion-contraction paths are also derived and characterized.

The D825 Modular Data Processing System is the result of a Burroughs study, initiated several years ago, of the data processing requirements for command and control systems. The D825 has been developed for operation in the military environment. The initial system,. constructed for the Naval Research Laboratory with the designation AN/GYK-3(V), has been completed and tested. This paper reviews the design criteria analysis and design rationale that led to the system structure of the D825. The implementation and operation of the system are also described. Of particular interest is the role that developed for an operating system program in coordinating the system components.

This paper appears in the March, 1972, issue of the Communications of the ACM. Its abstract is reproduced below.TENEX is a new time sharing system implemented on a DEC PDP-10 augmented by special paging hardware developed at BBN. This report specified a set of goals which are important for any time sharing system. It describes how the TENEX design and implementation achieve these goals. These include specifications for a powerful multiprocess large memory virtual machine, intimate terminal interaction, comprehensive uniform file and I/O capabilities, and clean flexible system structure. Although the implementation described here required some compromise to achieve a system operational within six months of hardware checkout, TENEX has met its major goals and provided reliable service at several sites and through the ARPA network.

This book represents an interesting attempt to take an overall view of a data system defined by the author as "the artifact that consists of a digital computer, a control program, and an accessible library of programs and data." His intended audience are professionals in the computer industry whose pursuit of specialized vocations leads them away from systematic consideration of the data system as a whole. His avowed aim is "crispness in style and frugality in detail." Consequently this book covers a good deal of ground—sometimes very briefly.

In 1934, when Yuen-Ren Chao discussed the nonuniqueness of phonemic solutions,' he demonstrated that different phonological analyses presuppose different underlying concepts. The thirty years since the publication of that paper have not produced any one phonological theory to which even most linguists will subscribe. The situation is not unusual in the history of science. Scientific theories are constantly submitted to change and revision; in an empirical science, the structure is never completed. Experiments become more precise, new phenomena are revealed, new concepts are developed. At all times we must be prepared to abandon our theory, remodel the foundations, and erect a new structure. But the history of science shows also that theories which turn out to be inaccurate can yet lead to the discovery of new facts; and each new theory retains some elements of the one it has supplanted. Acceptance of one theory does not require one to reject a rival theory in toto. It is in this spirit that the present paper attempts to describe certain characteristics of Twi phonology.2 It suggests that the incorporation of certain principles of the British system-structure or prosodic approach into the phonological component of a transformational grammar of Twi may provide a simpler and more revealing description. The phonological inventory of Twi, as it might look in a transformational grammar modeled after Morris Halle, The sound pattern of Russian,3 is presented in Tables 1 and 2 as a matrix of morphonemes and a branching diagram to represent them. According to this view, speech consists of a series of segments, specified by distinctive features (DF) and boundaries (#) characterized by their effect on the features.4