at a particular node, (b) breaks of one or more specific link(s), (c) massive failures, such as the New York area power blackout?

In general, with respect to areas of R & D concern affecting safeguarding and recovery provi sions, we may conclude with Davis that "Rarely, if ever, are measurements made of the ability of the system to respond when partially destroyed or malfunctioning, of the length of time required

for changing the system response to internal change in direction or to external stimuli, of the length of time necessary for a newcomer to be inserted into his assigned role in the system, of the redundancy, backup, or alternatives available at times of partial or total system destruction, and so forth. Clearly, there will be no adequately constructed system until such measures of effectiveness are understood and incorporated into system design." (Davis, 1964, p. 28).

Steadily mounting evidence of the nearly inevitable development of information-processingsystem networks, computer-communication utilities, and multiply-shared, machine-based, data banks illuminates a major and increasingly critical area of R & D concern. In this area, the problems of "organized complexity" 3.1 are likely to be at least an order of magnitude more intractable than they are today in multiprogrammed systems, much less in those systems requiring extensive manmachine interaction.

3.2

It is probable, in each of these three fields of development, that there has been and will continue to be for some time to come: (1) inadequate requirements and resources fact-finding and analysis, (2) inadequate tools for system design,3.3 and (3) the utter lack of appropriate means for evaluation in advance of extensive (and expensive) alternatives of system design and implementation.3.4 Certainly the problems of system networking will involve those of priority scheduling and dynamic allocation and reallocation in aggravated form.3.5 Moreover, the extensive prior experience in, for example, message-switching systems, is likely to be of relatively little benefit in the interactive system network.3.6

In particular, the practical problems of planning for true network systems in the areas of documentation and library services have scarcely begun to be attacked.3.7 Nevertheless, the development of computer-communications networks has begun to emerge as the result of some or all of the following factors:

"a. Load sharing among major computer cen

ters ..

“b. Data pick-up from remote test sites (or from airborne tests). In some cases real-time processing and retransmission of results to the test site would be desirable.

"c. Providing access for Plant A to a computer center at Location B. Plant A might have a medium-scale, small-scale, or no computer of its own.

"d. Data pick-up from dispersed plants and offices for processing and incorporation in overall reports. The dispersed points might be in the same locality as the processing center, or possibly as much as several thousand miles away." (Perlman, 1961, p. 209.)

Three special areas of system network planning may be noted in particular. These are the areas of network management and control, of distribution requirements, and of information flow requirements.

3.1. Network Management and Control
Requirements

Effective provisions for network management and control derive directly from the basic objectives and mission of the network to be established. First, there are the questions with respect to the potential users of the system such as the following:

1. What are the objectives of the system itself? Is it to be a public system, free and accessible to all? 3.11 Is it to serve a spectrum of clientele interests, privileges, priorities, and different levels of need-to-know? Is it subject, in the provision of its services, to constraints of national security, constitutional rights (assurance of protection of the individual citizen's right to the security, among other things, of his "papers" from unreasonable searches and seizures), laws and regulations involving penalties for violation such as "Secrecy of Communications," and copyright inhibitions?

2. What are the charging and pricing policies, if any, to be assessed against different types of service, different types of clients, and

different priorities of service to the different members of the clientele? 3.12

3. What different protections may be built into the system for different contributors with varying degrees of requirements for restrictions upon access to or use of their data? 3.13 4. What are the priority, precedence, and interrupt provisions required in terms of the clientele? 3.14

Next are the questions, in terms of the potential client-market, of the location, accessibility, cost, volume of traffic, and scheduling allocations for some determinate number of remote terminals, user stations, and communication links.

Then there are the questions of the performance and technological characteristics required with respect to these terminals, stations, and links.3.15 Are the central system and the communication network both capable of handling, effectively simultaneously, the number of individual stations or links required? Does the communication system itself impose limitations on bandwidths available, data transmission rates, number of channels operable effectively in parallel? Are alternate transmission modes available in the event of channel usurpation or nonavailability for other reasons? Is effectively on-line responsiveness of the communication system linkages required and if so to what extent?

More generally, the following design and planning questions should be studied in depth if there is to be effective management and control:

"1. What is the scope of the network?
a. Its geographical coverage

b. Services to be provided by and to whom
c. Location and facilities of participants
d. Existing capabilities available

e. Required rate of development

"2. What are the relevant software and data characteristics?

"6. What are the budgetary constraints and financially allowable rate of development?" (Davis, 1968, p. 4-5).

The factors of geographical coverage, location and facilities of participants, and membership point to some of the distribution requirements, to be considered next.

3.2. Distribution Requirements

A major area of concern with respect to distribution requirements in information processing network planning is that of the question of the type and extent of centralization or decentralization of the various system functions. There is first the possibility of a single master, supervisory, and control processing center linked to many geographically dispersed satellite centers (which carry out varying degrees of preprocessing and postprocessing of the information handled by the central system) and terminals. Secondly, several interconnected but independent processors may interchange control and supervisory functions as workload and other considerations demand.3.18 Still another possibility is regional centralization such has been recommended for a national documentation network, for example.3.19

Different compromises in network and system design to meet distribution requirements are also obviously possible.3.20 However, a variety of special problems may arise with respect to distribution requirements when some of the network functions are decentralized.3.21

Then there is the question of whether or not the network is to be physically distributed - that is, "the term 'distributed network' is best used to delineate those communications networks based on connecting each station to all adjacent stations, rather than to just a few switching points, as in a centralized network." (Baran, 1964, p. 5). This distribution requirement consideration is closely related to information flow analysis and planning, especially with respect to assurance of continuing productive operation when certain parts of the network are inoperative.3.22 It should be noted, moreover, that "solving the data base management problem has been beyond the state of the art." (Dennis, 1968, p. 373).

3.3. Information Flow Requirements

In general, it may be concluded that "to determine the correct configuration, certain basic factors must be investigated. These factors generally relate to the information flow requirements and include the following:

1. The kind of information to be transmitted through the communications network and the types of messages.

2. The number of data sources and points of distribution to be encompassed by the network and their locations.

3. The volume of information (in terms of messages and lengths of messages) which must flow among the various locations.

4. How soon the information must arrive to be useful. What intervals the information is to be transmitted and when. How much delay is permissible and the penalty for delays. 5. The reliability requirements with respect to the accuracy of transmitted data, or system failure and the penalty for failure.

6. How the total system is going to grow and the rate of growth.

(Probst, 1968, p. 19).

More specifically, overall system design considera

tions with respect to information flow requirements typically involve calculations of average daily volume of message and data traffic, peak loads anticipated, average message length, the number of messages to be transmitted in given time intervals, total transmission time requirements, and questions of variable duty cycles for different system and network components.3.23

Examples of relatively recent developments in this area include RADA (Random Access Discrete Address) techniques 3.24 and a "hot-potato" routing scheme for distributed networks.3.25 A continuing R & D challenge in terms of scientific and technical information services has been posed by Tell (1966) by analogy with the techniques of input-output economics.3.26 Of major concern is the problem of high costs of communication facilities necessary to meet network information flow requirements.3.27

The area of input-output, especially for twodimensional and even three-dimensional information processing, is currently receiving important emphasis in overall information processing system design. One reason for this, as we have seen, is the increased attention being given to remotely accessed, time-sharing, or man-machine interaction systems. In particular, as noted by Tukey and Wilk: "The issues and problems of graphical presentation in data analysis need and deserve attention from many different angles, ranging from profound psychological questions to narrow technological ones. These challenges will be deepened by the evolution of facilities for graphical real-time interaction. (Tukey and Wilk, 1966, p. 705).

4.1. General Input/Output Considerations

Since a multiplicity of input and output lines are assumed for a variety of types of information to be processed (including feedback information from users and from the system itself), development requirements with respect to both equipment and sortware processing operations include batching of various input units, buffering of at least some types of input (as required, for example, to provide necessary reformatting), and multiplexing of input operations. Such considerations also apply even more forcefully to interfaces between the various nodes of a network involving more than one type of participating system.4.2

Format control is typically needed both into and out of the system, preferably under dynamic program control. The format control subsystem, by means of address storage registers or other techniques, should enable the input data itself to determine where it should go in storage, and other means of "self-addressing" should be provided

without the need for elaborate or inefficient programming and related software requirements.4.

The overall output capability design should provide ability to reformat conveniently and efficiently 4.4 as well as to select certain character sequences. Because of the variety of equipments needed for various tasks, provision should be made for reversal of the bit order of input and output data so that either high or low order bits can be processed first. In the case of displays, special provisions may be required to prevent overlapping of symbols.4.5

Related to format control is the question of variable byte size for input and output. For the future, system design will require ASCII (American Standard Code for Information Interchange) code sorting and ordering capabilities, but in many circumstances it will also be necessary to handle collapsed subsets of ASCII and other codes, longer byte lengths such as 10- and 14-bit codes for typesetting, and even longer codes for monotype, numeric process control, data logging, and equipment control.

Analog-digital and digital-analog convertibility is needed for experimental applications in source data automation, measurements automation, map analysis, map and contour plotting, pattern processing, and the like. One example of convergent efforts in the field is provided by Ramsey and Strauss (1966) who discuss interrupt handling in the area of hybrid analog-digital computers as representative of more general on-line scheduling problems. For some of these investigations, at least virtual real-time clocks will be needed.4.6 This implies processor main frame and transfer trunks versatile enough to handle these requirements whether implemented by software or built into the hardware.

Another important requirement is for versatile and varied graphic input and output capability,

including light pen, microfilm, pen, microfilm, FOSDIC-type scanning, mark-sensing, OCR (Optical Character Recognition), MICR (Magnetic Ink Character Recognition), color-code input (such as Lovibond color network), and three-dimensional probe data in (see the first report in this series), and largevocabulary character and symbol generation; diagram retrieval, construction and reconstruction, and perspective or three-dimensional projection capabilities out (as discussed in the second report in this series). Photographic and TV-type input and output with good resolution, hard-copy reproduction capability, varying gray-scale facility, and at least the possibility of handling color input or output display techniques will be required in future system design.4.7 Audio input-output capabilities should include dataphone, acoustic signal inputs, and voice, with speech compression on output, requiring controlled timing of "bursts" or "slices."

In many system design situations, we should be able to switch peripheral equipment configurations around for special purposes and we may need to have multiple access to various types of peripheral devices simultaneously during the same processing run, e.g., to be able to shift between character recognition and graphic scanning tasks for input of material where text and graphics are intermixed.

Related to these problems of input, output, and on-line responsiveness (especially for clients involved in problem-solving applications), is the concept of graphical communication generally.4.8 This presupposes, first, a suitable language for the exchange of both pictorial data and control information between the designer and the machine, and secondly, provisions for the dynamic manipulation of data and controls.4.9

Recent programming techniques under investigation for the display of two-dimensional structure information are exemplified in work by Forgie,4.10 by Hagan et al. (1968) 4.11, and at the University of Michigan (Sibley et al., 1968).4.12 Then there is the DIALOG programming system developed at the ITT Research Institute in Chicago for graphical, textual, and numeric data input and display, online and offline programming facilities, and hard-copy options. (Cameron et al., 1967). A special feature is a character-by character man-machine interaction mode, so that the programmer may use only those input symbols that are syntactically correct. For more efficient machine use in production-type operations, a DIALOG compiler for the IBM 7094 has been prepared following the "Transmographer" of McClure.4.13 (McClure, 1965).

Then we note that "in the area of displays, determining the information to be displayed and generating the procedures for retrieval and formatting of the information are the difficult problems." (Kroger, 1965, p. 269). Further, as of today, "too many systems are designed to display all the

99

data, and not to display only the data needed for the decisions the system is called upon to make.' (Fubini, 1965, p. 2).

In general, the client of the on-line, graphical input-output, and problem-solving system needs convenient means for the input of his initial data, effective control of machine processing operations, effectively instantaneous system response, displays of results that are both responsive to his needs and also geared to his convenience, and handy means for the permanent recording of the decisions and design choices he has made.

With respect to these client desiderata, the identifiable R & D requirements relate to keyboard function key overlay design; 4.14 improvements in both problem-oriented and client-oriented languages for man-machine communication and interaction;4.15 fast, high-resolution, flicker-free display generation; 4.16 ability to selectively emphasize various areas of display,4.17 further development of the combination of static displays (such as maps) with computer-controlled dynamic displays,4.18 and rapid responsivity of the system to feedback from the client.

Since remote, reactive terminals are an increasingly important factor in systems involving dynamic man-machine interaction, the question of design of remote inquiry stations and consoles necessarily raises problems of human engineering for whose solution there is inadequate experimental cost-benefit, and motivational data 4.19 available to date. Also involved are questions of acceptance and interactive response by the client to feedback outputs from the system, including requests for further information or additional inputs and display of re-processed results.

4.2. Keyboards and Remote Terminal Design

Where graphic input and output facilities are to be available to on-line users, there are unresolved questions of interrelated and interlocking system and human factors. How clumsy are light pens or pointers to use? Are they heavy or difficult to aim? 4.20 Should light-pen imputs be displayed a little to the left or to the right of the actual lightpen location so that the active part of the input is not blocked from view by the moving light-pen itself? 4.21 Can flicker-rate be kept to a tolerable level without undue and costly regeneration demands on a multiply-accessed central processor used by the many clients, or must the remote terminal have storage and display re-generation capabilities at added cost and design complexity? 4.22 For graphic input and display should the input surface be flat, upright, or slanted? 4.23

It has been pointed out, in the case of the recent development of a solid state keyboard, that "the requirements of today's keyboards are becoming more complex. Increased reliability and more flexibility to meet specialized demands are essential. Remote terminals are quite often operated by

relatively untrained personnel and the keyboard must be capable of error-free operation for these people. At the same time it should be capable of high thru-put for the trained operator as will be used on a key tape machine.

"Some of the limitations of existing keyboards are: ● Mechanical interlocks which reduce operator speed.

● Excessive service (increasingly important for remote terminals).

Contact bounce and wear of mechanical switches.

● Non-flexible format." (Vorthmann and Maupin, 1969, p. 149).

For automatic typographic composition applications, it is emphasized that "the application of computers to typesetting only emphasizes the scope and the need for a radical re-thinking on keyset design," and that, although "one may imagine that the keyboard is a relatively simple piece of equipment . in fact, it presents a unique combination of mechanical, electrical and human problems." (Boyd, 1965, p. 152). Current R & D concerns with respect to keyboard redesign involve consideration of principles of motion study as applied to key positioning, key shape, key pressures required, and the like.4.24

Nevertheless, it is to be emphasized that “input-output devices are still largely the result of an ingenious engineering development and a somewhat casual and often belated attention to operator, system attachment, and programming problems” and that " no input-output device, including all terminals combined, has yet received the careful and competent human factors study afforded the cockpit of a military aircraft." 4.25 (Brooks, 1965, p. 89).

Beyond this are questions of design requirements for dynamic on-line display. Thus we are concerned with requirements for improved remote input console and terminal design.4.26 Relatively recent input-output terminal developments, especially for remote consoles or dynamic man-machine interaction, have been marked by improved potentialities for two- and even three-dimensional data processing and by further investigation of prospects for color, as discussed, for example, by Rosa (1965),4.27 Mahan (1968) 4.28 and Arora et al. (1967), among others. Van Dam (1966) has provided an informative state-of-the-art review of such scanning and input/output techniques. Vlahos (1965) considers human factor elements in three-dimensional display. Ophir et al. (1969) discuss computergenerated stereographic displays, on-line.4.29

In the area of input-output engineering and system design, what is needed for more effective manmachine communication and interaction will include the provision for remote consoles that are truly convenient for client use. Hardware, software, and behavioral factors are variously interrelated in

terms of desired display and console improvements.4.30

The desirable design specifications for remote inquiry stations, consoles, and terminals and display devices as discussed in the literature variously include: economy, dependability, and small enough size for convenient personal use.4.31 Some misgivings continue to be expressed on this score. Thus, it is reported that Project Intrex will consider the design of much more satisfactory small consoles 4.32 and Wagner and Granholm warn that "at the moment, it is difficult to predict whether remote personal consoles can be economically justified to the same extent that technological advances will make them feasible." (1965, p. 288). Cost certainly appears to be a major factor in the limited nature of the use that has been made of remote terminals to date.4.33

A second requirement is for the provision of adequate buffering facilities including, for at least some recent systems, capabilities for local display maintenance.4.34 From the hardware standpoint, it is noted that "the major improvements in displays will be in cost and in the determination and implementation of the proper functions from the user standpoint. The cathode-ray tube will probably be dominant as the visual transducer for console displays through 1970, but there are several new techniques for flat-panel, digitally addressed displays presently under development that may eventually replace the CRT in many applications. The advances in memory and logic component technologolies will permit significant improvements in the logic and memory portions of console displays." (Hobbs, 1966, p. 37).

4.35

Other features that are desirable may include a capability for relatively persistent display, for example, up to several hours or several days,4 and the capability, as in the Grafacon 1010 (a commercially available version of the RAND Tablet) for the tracing of material such as maps or charts to be superimposed on the imput surface, or the Sylvania Data Tablet ET 1, which also allows a modest third axis capability.

As in the case of system outputs generally, hard-copy options are often desired through the terminal device. For example, the console "should have a local storage device on which the user can build up a file of the pieces of information he is retrieving, so that he can go back and forth in referring to it. It should have means of giving him low-cost hard copy of selected material he has been shown and temporarily stored.” (King, 1965, p. 92).

The use of markers and identifiers for on-line text editing purposes should be simplified or eliminated to the maximum extent possible. If, for example, elaborate line and word sequence identifications must be used both by the machine system and by the client, then the virtues of machine processing for this type of application will be largely lost. Such systems should not only be easy to use, but easy to learn how to use.

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