Hierarchical Structure for Data Management

on a hierarchical organization of the data management control function and makes use of list processing concepts. Discussed are the separation of the logical and physical control functions as well as the data-element and operating-system controls. This hierarchical approach establishes a common basis for the creation, maintenance, and retrieval of data in direct-access storage. Logical functions express the control and management of generalized physical data structures; the physical leuel typically includes strings for data retrieval and maintenance. Cndirected graphs, and matrices derived from them, illustrate the data management relationships within the physical level. The same type of analysis may he used to show relationships between the hierarchical levels. The concept of list processing, or chaining, has been used as a technique for the manipulation of logical data strings for many years and has been formalized as a language' for handling data in computer storage. List processing has also been utilized with limited success for the control of data in direct-access storage devices. In general, when list structures are used for external data control, only a subset of the possible data structures is implemented , and the logical and physical relationships are approached as a single entity. Thus, the many ventures into this area are highly individualized, resulting in duplication and incompatibility. Consider various forms of list processing implicit within the SYSTEM/^^^ Operating System (os/36o)-access methods, compilers , and application packages. Such programs could be improved by a more formal discipline directed to the support of list data structures, particularly for data control where direct-access storage devices are used. Data structures and control functions that are possible on direct-access storage devices must be defined prior to the development of a data base that supports a language or access-method package. Historically, the utilization of direct-access devices has been approached from three levels: Device or channel program Access-method package Composite data-management systen On today's sophisticated equipment, programming at the device or channel level usually cannot be economically justified.