Showing papers on "Data access published in 1976"

Information storage facility with multiple level processors

Abstract: An information storage facility with multiple level processors for relieving one or more external host computers or intelligent terminals from conventional time consuming record searching functions, such as record formatting, indexing, buffering and the like. Three processor levels are provided: a communications level for handling external communications, a DBMS level for performing syntax scanning, hashing and coding/decoding routines, and data access functions e.g. indexing, searching, buffering, blocking, deblocking, storage management, and error recovery functions; and a storage level for performing data storage and retrieval, error recovery and storage device management. A direct memory access bus is also provided which enables high speed data transfer among the several processors included within the storage facility and also external host computers or intelligent terminals.

Information Secure Systems

Abstract: Publisher Summary By using a simple model it can be shown that an important part of an information secure system is the access control and privacy protection mechanism. Being represented as data in the data base, the information is rich in semantics. The semantically connected data structure has an overwhelming impact on the restrictiveness and complexity of the mechanisms. Restrictiveness is a measure of the amount of information denied to the user in the course of enforcing a security requirement and can be formalized in terms of protection precision. Complexity here is a reflection of the design and implementation difficulty of a mechanism in computer systems. The chapter formalizes these notions and illustrates them with examples. Five mechanisms of increasing complexity and decreasing restrictiveness (that is, increasing protection precision) are outlined. Some of their implementation considerations are discussed. Another mechanism, information-theoretic protection, is proposed as a solution to some of the problems of concealment protection. Some thoughts on information-theoretic protection are presented in an attempt to lay the groundwork for future study. Among mechanisms for concealment protection, it reports the advancement on attribute-based mechanisms, which protect data having one or more attributes in common. The advance in context protection is encouraging. Because context protection can enforce new access to data sets in a context where other data sets have been accessed, there is the need for access history keeping. Not only original and new access rights to the data sets (that is, text) must be remembered by the system, but the rights to the previously accessed data sets (that is, context) must also be recorded by the system. Access history keeping is therefore time consuming and space consuming in an information secure system. Nevertheless, this advance represents the first breakthrough in protection of semantically rich data bases.

Self-managing variable field storage system for handling nested data structures

Abstract: This disclosure relates to a storage system employing a serial periodic memory as the storage mechanism. The storage mechanism has one or more control and access ports which control data transmission to and from the storage mechanism, each port including input and output devices associated with a data track of the storage mechanism. A queue shift register is coupled between the input and output devices to receive previously stored information characters which are to be temporarily held when newly received information characters are to be written into the storage media. Control of the system resides in the control ports and is activated by commands from the external sources. A character set is employed which includes a beginning delimiter character and an ending delimiter character such that information segments may be of any length up to the capacity of the storage mechanism. The system control ports manage, among other things, the explicit representation of the beginning and end of strings of data and the decomposition of strings into substrings, the automatic allocation and reclamation of unused storage space as strings of data increase or decrease in size, and the permission or prohibition of access to data strings depending on the requestor's identity. Data strings may be accessed according to their order or by symbolic addressing.

Sparse matrix software

Abstract: In this paper we consider the problem of designing and implementing computer software for sparse matrix computations. We consider the data access requirements for typical sparse matrix computations, and review some of the main data structures used to meet these demands. We also describe some tools and techniques we have found useful for developing sparse matrix software.

An Investigation into Database Resilience

Abstract: Definitions In normal English usage the word resilience is taken to mean the power to resume original shape after compression; in the context of data base management the term data base resilience is defined as the ability to return to a previous state after the occurrence of some event or action which may have changed that state. The particular state of interest is the logical content of a data base. The physical state of the data base may also be of interest if access to the knowledge of this physical state is allowed to application programs. However this knowledge is increasingly denied to application programs in the attempt to preserve data independence (CODASYL, 1971) or to simplify data access by removing the need for navigation (Date and Codd, 1974) and thus returning to a previous logical state is often sufficient. One type of event or action expected is an error in the operation of the system. Hence a particular type of data base resilience of interest is the ability to return to a previous logical data base after the occurrence of an error which may have damaged the logical data base. Terms related to the concept of resilience are: privacy, security and integrity. Privacy is denned as 'whether or not a particular individual should have access to a specific piece of information' (Conway et al, 1972) and security as 'preventing unauthorised access to a file' (Dearnley, 1973). Integrity is defined as 'the safe-guarding by the system of information entrusted to it' (Wilkes, 1972). Thus data base resilience includes the ability to maintain integrity and a particular type of occurrence for which resilience is useful is the breaching of security with a subsequent unauthorised change to the data base. Similar definitions of these terms may be found in Browne (1972).

Improving Information Storage Reliability Using a Data Network

Abstract: : Backup and recovery methods using magnetic tapes are common in computer utilities, since information stored on-line is subject to damage. The serial access nature of the tape medium severely restricts the flexibility and simplicity of accessing and managing the stored data. A method using a data network is described, to present a backup mechanism which takes advantage of a large, inexpensive, random access remote data storage facility to provide data access and management functions that are more flexible than those provided by a traditional backup facility. Although data transfer rates will be reduced, data access and management will be simplified, and system availability will be improved. The work described is based on a network backup facility built for the Multics computer utility, using the ARPAnet.