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

What Services / Abstractionsdo we need?

• Look at some projects:– CLRC e-Science Centre – AstroGrid– MyGrid– ICENI– OGSA

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.

AstroGrid

VO=Virtual Observatory

MyGrid – Architecture

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

ICENI

• Low-level services– Computational

– Storage

– Software

– Networking

• High-level services– Application composition to define workflow

– Scheduling (mapping components to resources)

– Throughput (resource brokering)

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

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

Common Requirements?

• Low-level:– Security– Execution– Database Access– Data movement– Service Management

• High-level:– Workflow management (Scheduling)– Usage & Access Policy– Notification (Events & Messaging)