Showing papers on "Data access published in 1990"

NetCDF: an interface for scientific data access

Abstract: The network common data form (NetCDF), a data abstraction for storing and retrieving multidimensional data, is described. NetCDF is distributed as a software library that provides a concrete implementation of that abstraction. The implementation provides a machine-independent format for representing scientific data. Together, the abstraction, library, and data format support the creation, access, and sharing of scientific information. NetCDF is useful for supporting objects that contain dissimilar kinds of data in a heterogeneous network environment and for writing application software that does not depend on application-specific formats. Independence from particular machine representations is achieved by using a nonproprietary standard for external data representation. The discussion covers NetCDF data abstraction and interface; dimensions, variables, and attributes; direct access and hyperslab access, the NetCDF library; the data format; ncdump and ncgen utilities; experience, usability, and performance; limitations of NetCDF; and future plans. >

Automated procurement system with multi-system data access

Abstract: An automated procurement system, in which a buyer workstation is in communication with a mainframe database that stores global data relevant to procurement documents and reports The workstation is programmed with an interactive buyer interface that displays procurement documents, provides support data to aid in decision-making, and provides various document attachments Data is uploaded and downloaded to and from the mainframe and the workstation in a manner that is transparent to the buyer

Beyond the pale of MAC and DAC-defining new forms of access control

Abstract: Examples of DoD/intelligence data protection requirements are described that cannot be handled through traditional mandatory (MAC) or discretionary (DAC) access controls, and two new forms of access controls to respond to these problems are proposed. First, a user attribute-based access control for enforcement of dissemination controls is introduced. Second, a type of access control known as owner-retained access control is described, to provide a privilege-based form of access control that, unlike DAC, prevents access to data being extended to others without the owner's concurrence. For both types of controls, the access control rules to be enforced and the implications of providing automated enforcement of these controls are discussed. The two forms of control are compared, and an informal model is presented that provides a common framework for representing both. In conclusion, the benefits and drawbacks of this approach are discussed, and some areas for future work are identified. >

Multilevel locking system and method

Abstract: A multi-processor computer system in which each processor is under the control of separate system software and access a common database. A two level lock management system is used to prevent data corruption due to unsynchronized data access by the multiple processors. By this system, subsets of data in the database are assigned respectively different lock entities. Before a task running on one of the processors access data in the database it first requests permission to access the data in a given mode with reference to the appropriate lock entity. A first level lock manager handles these requests synchronously, using a simplified model of the locking system having shared and exclusive lock modes to either grant or deny the request. All requests are then forwarded to a second level lock manager which grants or denies the requests based on a more robust model of the locking system and queues denied requests. The denied requests are granted, in turn, as the tasks which have been granted access finish processing data in the database.

Query language execution on heterogeneous database servers using a bind-file bridge between application and database languages

Abstract: Application programs which are developed and scheduled within a first computing system environment are permitted to access relational data registered at a remote database management system (DBMS) operating in a second computing environment dissimilar to the first computing environment. Access to data through the DBMS from an application execution site remote from the DBMS is supported by a process, logically subordinate to the application program which maps application program data access requests to the DBMS.

Apparatus and method for providing private and shared access to host address and data spaces by guest programs in a virtual machine computer system

Abstract: A method and apparatus for providing common access to data spaces by a plurality of virtual machine guests emulated on a host computer system. A token received from a given one of the virtual machine guests is used to identify a particular host data space. The guest also supplies an offset. The offset and the identified host data space are then used to derive a host absolute address representative of a data location in the host data space.

Method and system for facilitating processing of statistical inquires on stored data accessible through a data access structure

Abstract: A data access structure facilitates the processing of statistical queries concerning records stored in the structure. The structure, according to the present invention, includes a plurality of data nodes storing the records, and a plurality of access nodes, each storing at least one pointer to another access node or to a data node, and arranged according to an organization whereby each access node is linked directly or indirectly to at least one data node. Statistical information is stored in or linked to the nodes of a subset of the plurality of access nodes and data nodes. The statistical information concerns the records stored in the data node or data nodes linked directly or indirectly to the respective nodes of the subset. Further, a software algorithm is provided responsive to changes in the records stored in the data nodes for updating the statistical information in the access structure concerning the records stored in the data node. The present invention is suitable for implementation with a wide variety of hierarchical and non-hierarchical access methods, including those based on the B-tree, ISAM, RRDS (Relative Record Data Set) of IBM VSAM, and HDAM of IBM IMS.

Method of protecting programs and data in a computer against unauthorized access and modification by monitoring address regions

Abstract: A method of protecting programs and data in computers against unauthorized access and modifications employs a programmable hardware circuit to monitor memory regions of a computer. The memory regions are divided into different access levels, and the circuit is programmed to permit access only to predetermined regions. If an unauthorized access is attempted by a program, an address corresponding to the program location initiating the unauthorized access is detected and the program is stopped. This ensures that the procedures for protecting the operating system cannot be circumvented to gain unauthorized access to data of any type. After programming of the circuit is completed, the programming cannot be changed except by actuation of a hardware switch or by re-starting the computer. Removal of the circuit will cause short circuits, thus making it impossible to shut the circuit off without being detected.

Multilevel secure database concurrency control

Abstract: The implications of multilevel security on database concurrency control are explored. Transactions are vital for multilevel secure database management systems (MLS/DBMSs) because they provide transparency to concurrency and to failure. Concurrent execution of transactions may lead to contention among subjects for access to data, which in MLS/DBMSs may lead to security problems. An abstraction of security models in terms of the transactions which they produce is presented. The notion of DC-Security which identifies a class of covert channels that are caused by contention for access to shared data, is introduced. This notion is useful for evaluating the security of transaction schedulers. A framework for multilevel secure schedulers which allows analysis of a schedulers' security properties at the protocol level is presented. Necessary and sufficient conditions are developed for DC-Security in this framework and proved using noninterference. A wide range of schedulers is evaluated against these conditions. >

A transient hypergraph-based model for data access

Abstract: Two major methods of accessing data in current database systems are querying and browsing. The more traditional query method returns an answer set that may consist of data values (DBMS), items containing the answer (full text), or items referring the user to items containing the answer (bibliographic). Browsing within a database, as best exemplified by hypertext systems, consists of viewing a database item and linking to related items on the basis of some attribute or attribute value.A model of data access has been developed that supports both query and browse access methods. The model is based on hypergraph representation of data instances. The hyperedges and nodes are manipulated through a set of operators to compose new nodes and to instantiate new links dynamically, resulting in transient hypergraphs. These transient hypergraphs are virtual structures created in response to user queries, and lasting only as long as the query session. The model provides a framework for general data access that accommodates user-directed browsing and querying, as well as traditional models of information and data retrieval, such as the Boolean, vector space, and probabilistic models. Finally, the relational database model is shown to provide a reasonable platform for the implementation of this transient hypergraph-based model of data access.

Data storage system with data mirroring and reduced access time data retrieval

Abstract: A data storage system with data mirroring and reduced access time data retrieval includes at least one pair of rotating data storage media each having a plurality of generally identical data records. Each rotating data storage medium includes position indicators, for providing one or more indications of the rotational position of each of the rotating data storage media with respect to its associated fixed position read/write mechanism. A position monitor receives the rotational position indications from each rotating data storage medium and computes and monitors the rotational position of each rotating storage medium with respect to its associated read/write mechanism. After receiving a request for access to one or more data records stored on the pair of rotating data storage media, the system computes projected data access times for retrieving the requested data record on each of the rotating data storage media, and commands retrieval of the requested data record to the rotating data storage medium having the shortest projected data access time based on the rotational position and state of the respective data storage medium.

Time capsules: an abstraction for access to continuous-media data

Abstract: The author presents the time capsule abstraction to describe how timed data shall be stored, exchanged, and accessed in a real-time system. When data are written into a time capsule, a time stamp and a duration are associated with the data item. When it is read, a time stamp is used to select the data item. The time capsule abstraction includes the notion of clocks that ensure periodic data access that is typical for continuous-media applications. By modifying the parameters of a clock, effects such as time lapses or slow motion can be achieved. >

Performance Evaluation of Parallel Programs in Parallel and Distributed Systems

Abstract: This paper deals with performance evaluation of parallel and distributed systems based on monitoring of concurrent interdependent activities. First a model is introduced for describing the dynamic behavior of computer systems in terms of events. Then, a distributed hardware/hybrid monitor system based on event driven monitoring and its tool environment SIMPLE are presented. We emphasize the tool environment as a prerequisite for successful performance evaluation. The tool environment for evaluating event traces, which integrates the data access interface TDL/POET and a set of evaluation tools for processing the data, makes evaluation independent of the monitor device(s) and the object system. It provides a problem oriented way of accessing event traces.

A Secure RISC-based Architecture Supporting Data Persistence

Abstract: The MONADS project has as its principle aim the investigation of techniques for the development of secure and reliable computer systems. However, unlike many other comparable projects we have not limited our investigations to software, but have sought solutions in terms of an integrated architecture involving both hardware and software. We begin by describing the MONADS architecture and show how it supports protected information-hiding modules and persistence in an in-process environment. From this discussion we derive four requirements of a physical implementation of the architecture. We then describe the MONADS-MM implementation and demonstrate how a conventional RISC processor can be used as the basic processing element of a system meeting these requirements. The resulting system provides fine-grain control over access to data and inherent support for persistence. An additional feature of the MONADS-MM design is support for a main memory of up to 64 gigabytes.

Image forming/storing apparatus which can store image data and can efficiently perform document filing

Abstract: Image data is converted into digital data and is read by a scanner (41) The digital data read by the scanner (41) is stored in an optical disk (233) Retrieval data (802, 805) representing the storage position or the like of the data stored in the optical disk (233) is also recorded in the optical disk (233) In addition, paper (P) on which abstract image data of the digital data stored in the optical disk (233) is recorded is output from a printer (43) The respective components of the invention are integrally arranged This arrangement can simultaneously enjoy both the advantages of a paper file and an electronic file, ie, quick data access and a large storage capacity More specifically, a plurality of sheets of document data are replaced with at least one sheet of paper (P) on which simple abstract image data is recorded and image data stored in an optical disk (233), thus allowing easy registration and retrieval of image data of documents and enabling a great reduction in space for documents In addition, since document retrieval is performed on the basis of paper having abstract data recorded thereon, a high data access speed, which is the advantage of a paper file, can be maintained

Interproceessor Invocation on a NUMA Multiprocessor

Abstract: On a distributed shared memory machine, the problem of minimizing accesses to remote memory modules is crucial for obtaining high performance. We describe an object-based, parallel programming system called OSMIUM to support experiments with mechanisms for performing invocations on remote objects. The mechanisms we have studied include: non-cached access to remote memory, data migration, and function-shipping using an interprocessor invocation protocol (IIP). Our analyses and experiments indicate that IIP competes well with the alternatives, especially when the structure of user programs requires synchronized access to data structures. While these results are obtained on a NUMA multiprocessor, they are also applicable to systems that use hardware cache coherency techniques.

Operating system and data base

Abstract: A system for program development and execution consisting of a high level programming language based on a four part rule organization (31), consisting of a rule definition, a list of conditions, a list of actions taken upon satisfaction of a corresponding condition, and a list of exception handlers. Data access events are supplied through a table access method (21) which provides an interface to the variety of sources of data (22-30) coupled to the system. A table data store (103) organizes data in an object oriented, relational system, where each table is ordered on a primary key (502). The table access method (21) performs selection and ordering operations on the tables accessible through the table access method (21), implements and triggers invalidation routines upon data access events, and provides a common view of data stored across heterogeneous data stores coupled through servers (203-205) to the table access method (21). Ordered tables (103) are subdividable by additional parameters associated with table names.

Exploiting trade-offs in the design of fault-tolerant distributed databases

Abstract: In a fault-tolerant distributed database, data replication can improve the availability of data as well as the response times of transactions, but only to a point. More replication can limit concurrency of transaction execution in the event of communication failures that partition the database. It can also increase the execution time of the replica management protocols. In fact, there are trade-offs involved between the amount of replication, the availability of data, and the transaction response times; the trade-offs are a function of the failure characteristics and the transaction access patterns. This work focuses on analyzing the nature of these trade-offs and develops strategies for exploiting them to enhance system performance. First, the trade-offs between replication and availability are statically analyzed--where it is assumed that the underlying communication network has partitioned into several groups--and upper bounds on availability are derived for different cases of data replication and data access patterns. It is shown that partial replication can improve availability despite partition failures, if the partitioned database satisfies a particular property of data access. To ensure that a database indeed satisfies this property with a high probability, a network design strategy is developed. This is done by first identifying the most desirable partition of the set of sites--one characterized by high transaction access within every group of the partition, and low access across the groups--for a given cost of connecting the database sites, and then defining the connectivity of the database in a hierarchical manner. While the problem of finding the most desirable partition is shown to be NP-hard under most natural definitions of desirability, excellent approximation algorithms exist for finding such a partition. The resulting parameterized network, called a Harary Network, can support a wide spectrum of database assumptions and behaviors. Finally, to analyze the dynamic performance of such a database, in particular the trade-offs between availability and response times, a stochastic tool is developed. This tool enables a database designer to perform an analysis of the expected system performance and fine-tune the system parameters for improved performance. As an example, we extend Thomas's majority consensus protocol to tolerate both site and link failures and analyze its performance using our stochastic tool.

Partitioning Programs into Processes

Abstract: A technique is presented to implement a UNITY program [CM88] as a set of processes on a MIMD-architecture. The approach is based on the identification of specific data access patterns between statements. They give hints on the decomposition of the program into processes.

Transplant information management system: a center-oriented approach to transplant data management.

Abstract: TIMY is the ideal management system for novice data-entry personnel as well as for the research staff, nurses, and physicians at our facility. Access to data through the use of menus and security systems makes TIMY a user-friendly database. It has excellent data export capabilities so that more complex data analysis can be performed using dedicated software such as SPSS/PC, BMDP, or SAS. This provides great flexibility as well as the power needed for the study of complex data sets.

Sharing persistent object-bases in a workstation environment

Abstract: This dissertation provides a framework to study the problem of sharing information in a network of highly autonomous workstations. It focuses on providing the necessary basic support for accessing shared information, and provides a framework to study other forms of synchronized sharing. This thesis introduces WorldBase, a system for storage and access of distributed, possibly inconsistent object-bases. WorldBase supports a user environment with richly structured access to data from more than one object-base. Each information repository, called a world database (or simply a world), contains a cluster of related structured information and is a basic unit for sharing information across a network. In addition to presenting the overall architecture of WorldBase, this thesis also describes mechanisms provided for: selecting information from worlds and underlying databases, transforming data from one schema to another, and merging the data in two or more worlds to create a new world. A world is a unit for conceptual grouping, focusing, communicating and sharing of information. Each world has a world schema specification, and a collection of other specifications that constrain the world. The world schema specification specifies the schema of objects and relationship in the world. The world schema specification and other specifications constrain a world's population and express some of its semantics. WorldBase provides a "file-like" paradigm to deal with worlds. It uses the virtual memory of a workstation to provide a WorldBase workspace with which the user interacts. The user has access to collections of worlds and their specifications in persistent store but cannot access their contents directly. Loading a world from persistent memory to a workspace activates the world so its contents can be accessed by the user. The user may load multiple worlds into a workspace, effectively merging them. Hence, WorldBase allows users to maintain consistent object-bases in virtual memory, while accommodating inconsistent, autonomous object-bases in persistent stores. (Copies available exclusively from Micrographics Department, Doheny Library, USC, Los Angeles, CA 90089-0182.)

Processing system for decentralized data base

Abstract: PURPOSE:To shorten the total processing time of the title system by producing a secondary condition tree based on the access requests of users, carrying out the data base processing related to each secondary condition via the corresponding host computer system, and completing the data base processing to the access request of the user after obtaining only the result of the data base processing carried out by the host computer system. CONSTITUTION:A condition tree production means 12 converts an access request into a condition three consisting of the secondary conditions in a host computer system 1 which accepts the access requests from users. Then a decentralized data access means 14 requests the data base processing related to the secondary conditions of the condition tree to the system 1 containing the corresponding data base. A decentralized data base control means 11 acquires the results of the data base processing related to the secondary conditions from other host computer systems 2 and 3 and then completes the data base processing against the access request to output an answer.

Test control apparatus.

Abstract: The data controller (4) is connected to test equipment (2) and a user interface (6) to create all the data files, including files for seizures test data, instructions test or the sample identification code. These data files are created independently of the processing controller (5) and the format of the instrument data file (2). The processing controller (5) uses a program library (9) for facilitating the processing of data retrieved from the data files by the data controller (4) to produce test reports to the output interfaces (7) . Data access is relatively fast because the data controller (4) sets of memory data in the active and record separate databases (15 and 17).

Multimedia data management system

Abstract: PURPOSE:To easily and unitarily manage shape and spatial information and attribute information related to one thing by managing the shape and spatial information by a buffer chain having a fixed length and giving attributes for respective units of things to a relation data base. CONSTITUTION:Thing information is stored in a graphic master file 1 expressed with vectors using coordinate values and a picture data file 3 expressed with dots and managed by the buffer chain having the fixed length. Further, the attribute information is expressed with codes and character data and stored in an attribute data file 2 tupling an object and attributing the classifications of the attributes. These three types of data are linked by an identifier to identify the thing, and the relations between the things are expressed with a data structure having the pointering format of a fixed-length buffer with the identifier as its object. Thus, graphic data, picture data, and attribute data can be easily unitarily managed, and data management and data access can be executed unitedly.

Balancing Data Access and Data Protection: The Luxembourg Income Study Experience

Abstract: The purpose of this paper is to describe the development and current status of the LIS project with emphasis on the systems that manage and monitor access to the database.

Shared data processing system between programs

Abstract: PURPOSE:To enable programs executed in parallel to always correctly process shared data without contradictions by providing only one data buffer for the purpose of accessing shared data by plural programs. CONSTITUTION:At the time of simultaneous processing of programs X 11 and Y 21, processing 11-2a sends data, which means that shared data A 51 should be increased by two, to a data buffer 70. Meanwhile, the program Y 21 sends data, which means that shared data should be increased by three, by processing 21-2a to the data buffer 70. A shared data access program 61 analyzes contents of a first sent telegraphic message X by processing 61-1 and increases the value of shared data A 51 by two to set it to 102. Though another telegraphic message Y is sent during the operation of the shared data access program 61, it is not erased but is left in the buffer 70 to wait for the end of processing of the telegraphic message X.

Program control system

Abstract: PURPOSE:To efficiently use an address space to prevent reduction of the speed due to reallocation and duplicating of shared data by storing data area sizes of respective programs, the address of shared data accessed by respective codes, and starts addresses of respective data in a conversion table. CONSTITUTION:When plural programs are loaded by the program control system, programs A and B are loaded to separate addresses on a memory, and loaded programs are divided to codes and data 1. Sizes of areas of data 2 are set by referring to areas of data 1 in initializing routines in codes. Area sizes of data 2 of respective programs which are obtained by calculation, the address of shared data accessed by respective codes, and start addresses of respectively data 2 are stored in the conversion table. In a step 5 of program recoupling, addresses of shared data access parts in codes A and B are converted to addresses from the start address of shared data in the conversion table.