Data access

About: Data access is a research topic. Over the lifetime, 13141 publications have been published within this topic receiving 172859 citations. The topic is also known as: Data access.

Encryption-based data access management

Abstract: Encryption-based data access management may include a variety of processes. In one example, a device may transmit a user authentication request for decrypting encrypted data to a data storage server storing the encrypted data. The computing device may then receive a validation token associated with the user's authentication request, the validation token indicating that the user is authenticated to a domain. Subsequently, the computing device may transmit the validation token to a first key server different from the data storage server. Then, in response to transmitting the validation token the computing device may receive, from the first key server, a key required for decrypting the encrypted data. The device may then decrypt at least a portion of the encrypted data using the key.

Representing and reasoning about semantic conflicts in heterogeneous information systems

Abstract: The scCOntext scINterchange (scCOIN) strategy (Sciore et al., 1994, Siegel and Madnick, 1991) presents a novel perspective for mediated data access in which semantic conflicts among heterogeneous systems are not identified a priori, but are detected and reconciled by a Context Mediator through comparison of contexts associated with any two systems engaged in data exchange. In this Thesis, we present a formal characterization and reconstruction of this strategy in a scCOIN framework, based on a deductive object-oriented data model and language called scCOIN. The scCOIN framework provides a logical formalism for representing data semantics in distinct contexts. We show that this presents a well-founded basis for reasoning about semantic disparities in heterogeneous systems. In addition, it combines the best features of loose- and tight-coupling approaches in defining an integration strategy that is scalable, extensible and accessible. These latter features are made possible by teasing apart context knowledge from the underlying schemas whenever feasible, by enabling sources and receivers to remain loosely-coupled to one another, and by sustaining an infrastructure for data integration. The feasibility and features of this approach have been demonstrated in a prototype implementation which provides mediated access to traditional database systems (e.g., Oracle databases) as well as semi-structured data (e.g., Web-sites). (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

Improving cache performance in dynamic applications through data and computation reorganization at run time

Abstract: With the rapid improvement of processor speed, performance of the memory hierarchy has become the principal bottleneck for most applications. A number of compiler transformations have been developed to improve data reuse in cache and registers, thus reducing the total number of direct memory accesses in a program. Until now, however, most data reuse transformations have been static---applied only at compile time. As a result, these transformations cannot be used to optimize irregular and dynamic applications, in which the data layout and data access patterns remain unknown until run time and may even change during the computation.In this paper, we explore ways to achieve better data reuse in irregular and dynamic applications by building on the inspector-executor method used by Saltz for run-time parallelization. In particular, we present and evaluate a dynamic approach for improving both computation and data locality in irregular programs. Our results demonstrate that run-time program transformations can substantially improve computation and data locality and, despite the complexity and cost involved, a compiler can automate such transformations, eliminating much of the associated run-time overhead.

SABIO-RK—database for biochemical reaction kinetics

Abstract: SABIO-RK (http://sabio.h-its.org/) is a web-accessible database storing comprehensive information about biochemical reactions and their kinetic properties. SABIO-RK offers standardized data manually extracted from the literature and data directly submitted from lab experiments. The database content includes kinetic parameters in relation to biochemical reactions and their biological sources with no restriction on any particular set of organisms. Additionally, kinetic rate laws and corresponding equations as well as experimental conditions are represented. All the data are manually curated and annotated by biological experts, supported by automated consistency checks. SABIO-RK can be accessed via web-based user interfaces or automatically via web services that allow direct data access by other tools. Both interfaces support the export of the data together with its annotations in SBML (Systems Biology Markup Language), e.g. for import in modelling tools.

Specifying and enforcing access control policies for XML document sources

Abstract: The Web is becoming the main information dissemination means in private and public organizations. As a consequence, several applications at both internet and intranet level need mechanisms to support a selective access to data available over the Web. In this context, developing an access control model, and related mechanisms, in terms of XML (eXtensible Markup Language) is an important step, because XML is increasingly used as the language for representing information exchanged over the Web. In this paper, we propose access control policies and an associated model for XML documents, addressing peculiar protection requirements posed by XML. A first requirement is that varying protection granularity levels should be supported to guarantee a differentiated protection of document contents. A second requirement arises from the fact that XML documents do not always conform to a predefined document type. To cope with these requirements, the proposed model supports varying protection granularity levels, ranging from a set of documents, to a single document or specific document portion(s). Moreover, it allows the Security Administrator to choose different policies for documents not covered or only partially covered by the existing access control policies for document types. An access control mechanism for the enforcement of the proposed model is finally described.