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 / Abstractions
do we need?
• Look at some projects:
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CLRC e-Science Centre
AstroGrid
MyGrid
ICENI
OGSA
CLRC e-Science Centre
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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
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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
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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:
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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
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Distributed Data Management
Work flow
Auditing
Instrumentation & monitoring
Problem determination (e.g. dump, trace & log)
Security protocol mapping
Common Requirements?
• Low-level:
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Security
Execution
Database Access
Data movement
Service Management
• High-level:
– Workflow management (Scheduling)
– Usage & Access Policy
– Notification (Events & Messaging)