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Abstraction Layers

This document explores the significance of abstraction layers in e-Science services, distinguishing between low-level and high-level services from the perspectives of both computer and working scientists. It discusses the need for protection against changes, the role of protocols like SOAP, and the implementation of services including authentication, resource discovery, and more. The document highlights various projects like AstroGrid and MyGrid, outlining their architectures and workflows to illustrate effective service composition and management.

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Abstraction Layers

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  1. Abstraction Layers • Why do we need them? • Protection against change • Where in the hourglass do we put them? • Computer Scientist perspective • Expose low-level services • Use SOAP as a wire protocol? • Working Scientist perspective • Want high-level services • Use C/C++/Java APIs • Opaque Service & Interaction Handles

  2. What Services / Abstractionsdo we need? • Look at some projects: • CLRC e-Science Centre • AstroGrid • MyGrid • ICENI • OGSA

  3. CLRC e-Science Centre • Single sign-on authentication • Security service • Authorisation • Additional user services (including local user management) • Resource discovery service • Workspace creation service • 3rd party file transfer facility • XML parser service • Query generation • Replication • Data source discovery • Results collation • Dynamic resource monitoring • Event handling services • Messaging service • Job submission • Job monitoring • Visualisation • Computational steering • Thesaurus service • Ontology service.

  4. AstroGrid VO=Virtual Observatory

  5. MyGrid – Architecture

  6. MyGrid Services • User Agent & Repository • Notification • Workflow: Personalisation, Resolution, Enactment & Serialisation • Databases & Distributed Query • Job Scheduling & Resource Management • Information Extraction • Authentication • Service Directory • User, Group & Roles Directory • Workflow Provenance & Repository • Ontologies – Service function & metadata

  7. ICENI • Low-level services • Computational • Storage • Software • Networking • High-level services • Application composition to define workflow • Scheduling (mapping components to resources) • Throughput (resource brokering)

  8. OGSA (17/2/02) • Is a Grid Service also a Web Service? • YES as it has ports (described in WSDL) for: • Grid Service (Introspection & termination) • Notification Source & Sink • Registration of Grid Service Handles • Service creation (factory) • Primary Key (map key to GSH) • Mapping (map GSH to GSR) • BUT can only be deployed in an OSGA compatible hosting environment • Is a Web Service also a Grid Service? • NO as it ‘misses’ out on the extra capability • BUT can be deployed within an OGSA environment

  9. OGSA Services • Low-level services • Execution, file transfer & service meta-data (?) • Higher-level services • Distributed Data Management • Work flow • Auditing • Instrumentation & monitoring • Problem determination (e.g. dump, trace & log) • Security protocol mapping

  10. Common Requirements? • Low-level: • Security • Execution • Database Access • Data movement • Service Management • High-level: • Workflow management (Scheduling) • Usage & Access Policy • Notification (Events & Messaging)

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