The emergence of a database technology in recent years has focused interest on the subject of data models. A data model is the class of logical data structures which a computer system or language makes available to the user for the purpose of formulating data processing applications. The diversity of computer systems and languages has resulted in a corresponding diversity of data models, and has created a problem for the user in selecting a data model which is in some sense appropriate to a given application. An evaluation procedure is needed which will allow the user to evaluate alternative models in the context of a specific set of applications. This paper takes a first step toward such a procedure by identifying the attributes of a data model which can be used as criteria for evaluating the model. Two kinds of criteria are presented: use criteria, which measure the usability of the model; and implementation criteria, which measure the implementability of the model and the efficiency of the resulting implementation. The use of the criteria is illustrated by applying them to three specific models: an n -ary relational model, a hierarchic model, and a network model.

The time and cost of implementing data processing applications can be greatly reduced through the use of software systems which provide language for the expression of file-level operations on data, i.e., operations whose operands are sets of records or entire files, such as report generation and sorting. Such systems, which have been referred to as self-contained systems or generalized file management systems, have characteristically been restricted to logical data structure classes no richer than hierarchies. This paper explores the extension of the concept of file-level operations to network structures, as exemplified by the CODASYL DDLC data structure class, on the assumption that such a facility will prove useful to certain types of users (e.g., data administrators) for certain types of data manipulation (e.g., data base creation and updating). The paper first outlines the general requirements which must be met in such a facility, and then describes a specific approach to the development of a language for such a facility.

This paper gives a description of the "virtual machine" of MULTICS, the multiple-user computer system conceived at M.I.T. and implementedfdhuf on the General Electric Model 645 time-sharing computer. The virtual machine is the machine which is seen by the system "user," i.e., the application programmer working at the assembly language level. The MULTICS virtual machine has a number of salient features which distinguish it from conventional machines.

article Free AccessGeneralization: Key to Successful Electronic Data Processing Author: W. C. McGee General Electric Co., Hanford Atomic Products Operation, Richland, Wash. General Electric Co., Hanford Atomic Products Operation, Richland, Wash.View Profile Authors Info & Claims Journal of the ACMVolume 6Issue 1Jan. 1959 pp 1–23https://doi.org/10.1145/320954.320955Published:01 January 1959Publication History 17citation950DownloadsMetricsTotal Citations17Total Downloads950Last 12 Months85Last 6 weeks8 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF