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Technologies

Grid Technologies

OGSA and OGSI

The Open Grid Services Architecture (OGSA) is designed to facilitate the interoperability among different Grid deployments, which aligns Grid technologies with Web Services technologies, and introduces a service-oriented paradigm into the Grid. The first formal and technical specification of OGSA is the Open Grid Services Infrastructure (OGSI). Currently, OGSI is evolving towards the Web Services Resource Framework (WSRF) to embrace new Web Services standards. OGSA and OGSI OGSA adopts a common representation for all resources (e.g., computational and storage resources, programs, databases): each resource in OGSA is represented as a Grid service, i.e., aWeb service that provides a set of well-defined interfaces and follows specific conventions.

OGSA-DAI/DQP

Both OGSA-DAI and OGSA-DQP build upon OGSA. The main objective of OGSA-DAI/DQP is to provide a uniform service interface for data access and integration over the Grids. OGSA-DAI extends Grid services with new services and portTypes for individual data access, such as Grid Data Service (GDS), Grid Data Transport (GDT), Grid Data Service Factory (GDSF), and DAI Service Group Registry (DAISGR). OGSA-DQP extends OGSA-DAI with two new services (and their corresponding factories) for distributed query processing over multiple data sources: a Grid Distributed Query Query Service (GDQS) which compiles, optimises, partitions and schedules distributed query execution plans over multiple execution nodes in the Grids, and a Grid Query Evaluation Service (GQES) which is in charge of a partition of the query execution plan assigned by a GDQS.

P2P Technologies

P2P technologies share the same final objective as Grid, i.e., to pool large sets of resources, however,they address different requirements and thus have different design approaches. In general,P2P technologies focus more on decentralization and scalability, while Grid technologies focus more on providing various complex services.

Three main classes of P2P systems have emerged so far: distributed computing, file sharing, and collaborative, among which, file sharing systems is the most studied. Based on whether there is any constraint on network topology or on data placement, file sharing systems are further classified into two main kinds: unstructured or structured. Our work is most related to super-peer networks, one kind of unstructured network, which strikes a balance between the inherent search efficiency of centralized systems and the robustness of decentralized systems. These kinds of networks can take advantage of the heterogeneity among the capabilities of participating peers. In a super-peer network,some peers with more capability (e.g. more bandwidth or CPU) take on the role of super-peers, and act as servers to a set of clients (peers with less capability) in the network.

Data Integration Technologies

Traditionally, in the database community, data integration systems are characterized by an architecture based on a global schema and a set of sources, and a crucial aspect in these systems is modelling the relation between the sources and the global schema. Two approaches has been proposed: one is global-as-view (GAV), where the global schema is expressed in terms of the sources; the other is local-as-view (LAV), where each source is defined as a view over the global schema. Regardless of the approach used, during query processing, a query posed over the global schema needs to be reformulated in terms of a set of queries over the sources.

Large-scale Data Sharing Technologies

Semantic Web/Grid Technologies

  • OWL
  • RDF
  • Jena
  • FOAF