TAG(ID:7156/tag002)
for Time Automated Grid system
Automated programming system from IBM
Related languages
| TAG | => | PSL | Incorporated some features of |
References:
TAG
Developed in 1962 by D. H. Meyers, of IBM's System Research Institute, TAG was automated in 1966. To use the Time Automated Grid system, the analyst first recorded the system output requirements. Inputs were examined during later iterations of the program.
Once the output data requirements were fed into the system, TAG worked backward to determine what inputs were necessary and at what point in time. The result was the definition of the minimum data base for the system. With the aid of the reports gencrated by TAG, the analyst systematically resolved the question of how the required inputs were to be entered into the data flow. This approach enabled him to concentrate on pertinent input elements and to bring them into the system at the proper place. Superflous or repetitious data were identified and eliminated from the system. Discrepancies in the use of any data element were corrected.
When both inputs and outputs were defined to TAG, the next iteration of the program produced file format and systems flow descriptions. File contents and data flow were both based upon time--the time at which data elements entered the system and the time at which they were required to produce output.
To TAG, the elapsed time between these two moments created the need for files. The files defined by TAG indicated what data must be available in each time period to enable the system to function. The job definition depicted the flow of these files, as well as that of the inputs and outputs, within and between time cycles. This approach provided an overview of the system, showing the interrelationship of all data in the system.
Knowing these interrelationships made it possible for the systems analyst to determine whether the outputs desired were quickly and easily obtained, and thus economically justified. With knowledge of the availability of data elements in given time periods, the analyst determined where additional useful outputs might be obtained.
The upper portion of Figure 13 shows the principal form used for TAG. The form was divided into two horizontal sections, one for requirement titles, the other for data names. The characteristics of the input, output, or file being described were recorded in the requirements title section. Comments on the data requirements of the input, output, or file were detailed in the data name section.
The output of the TAG system was a series of ten reports that documented input, analyzed data requirements, and provided file and data flow definition. The key report was the time-grid analysis, which traced the appearance of each data element, by time, through all the requirements in the system (shown in the lower portion of Figure 13).
The grid indicated those data elements that must be carried in files, enabling the analyst to identify the minimum data base requirements. The other nine reports were: time/key analysis, user data, glossary of data names, document analysis, sorted list of data names, summary of unresolved conditions, serial file records, direct access records, and job definition.
The development of this semi-automated technique was significant in the evolution of systems analysis techniques.
Extract: ADS and TAG
ADS (Lynch, 1969) and TAG (IBM) basically consist of a set of forms describing an entire application which are filled out by the user
or system analyst and then machine-analyzed for use by programmers and file designers. If the forms could be translated to working programs, then we would actually have an extension of RPG concepts
from a single program to a whole set of programs, i.e., a full application or system.
in Proceedings of the ACM SIGPLAN symposium on Very high level languages, March 28-29, 1974, Santa Monica, California, United States view details
Historical and Technical Background
To meet the needs outlined above, the Information Systems Design and Optimization System (ISDOS) Project at the University of Michigan has been studying the systems building process with the objective of developing a methodology for computer-aided design and construction of information systems. A description of the ISDOS Project can be found in Teichroew and Sayani [9].
ISDOS was born at Case Institute of Technology (now Case-Western Reserve University) in 1967 and was moved to the University of Michigan in 1968. Affiliation with Purdue University is also maintained through the efforts of Dr. Jay F. Nunamaker, an original member of the ISDOS Project at Case. The work at ISDOS has involved both the study of existing techniques for requirements statement and the development of new Requirements Statement Languages. All techniques view the problem in essentially the same way. They describe how to produce outputs from inputs. All techniques provide some method for describing data relationships as the user views them. They provide some facility for stating the requirements of the problem. Several provide some facility for stating other data such as time and volume.
Young and Kent [i0] represent the earliest work. Information Algebra is the work of the CODASYL Development Committee [ii]. Two other efforts have been reported by Langefors [12 and 13] and Lombardi [14]. Accurately Defined Systems (ADS) is a product of the National Cash Register Company (IS] and is described by Lynch [16]. The Time Automated Grid (TAG) system, a product of IBM, was developed by Myers [17] and is described by Kelly [18].
ADS and TAG use a practical, straightforward approach without attempting to develop any "theory" of data processing. ADS and TAG are systematic ways of recording the information that a systems analyst would gather. ADS or TAG could be used by any experienced systems analyst with very little instruction.
Young and Kent and Information Algebra represent a problem definition approach that is more concerned with developing a theory. Both use a terminology and develop a notation that Xs not at all natural to most analysts.
Lombardi's approach requires the completion of the system design before it can be used and resembles a non-procedural programming language rather than an RSL. However, Lombardi's work is relevant because it presents a non-procedural technique for stating requirements once the file processing runs have been determined. Langefors' technique uses the concept of precedence relationships among processes and files without indicating how these relationships are obtained and is relevant to the analysis of a problem statement rather than to the design of a system. However, it does suggest a number of desirable features of a requirements statement technique.
Despite the availability of these RSL techniques, their use has not been extensive. To the best of our knowledge, the languages of Young and Kent and of Lombardi have not been used except in an experimental way. Information Algebra has been used only once by Katz and McGee [19]. It appears that the development and use of TAG has been discontinued by IBM. ADS appears to be gaining in user acceptance. The U. S. Navy [20], in the process of designing a financial system, and a number of other firms [21] have used ADS as a requirements statement technique.
This current work is the result of an evolutionary process involving several different RSL's.
The first development SSL/I (SODA Statement Language/I) is the work of Nunamaker [22]. SODA (Systems Optimization and Design Algorithm) is an ISDOS software component that produces specifications for program module and storage structure and for hardware selection from the requirements analyzed by an RSA. Extension of SSL/I resulted in the development of PSL/I (Problem Statement Language/I) described by Koch, Krohn, McGrew, and Sibley [23]. Experience with PSL/I indicated its shortcomings and led to PSL/II possessing improvements suggested by Hershey, Rataj, and Teichroew [24]. Simultaneous with the development of PSL/II, experience with ADS demonstrated the value of a forms-oriented RSL for ease of requirements statement.
in Proceedings of the 1974 ACM Annual Conference San Diego, November, 1974 view details