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Abstraction Layers

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

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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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