SeLeNe - Architecture

George Samaras

Kyriakos Karenos

Larnaca – April 2003

THE UNIVERSITY OF CYPRUS

SeLeNe – University of Cyprus

Presentation Preview

• Introduction – Service-based Approach

• SeLeNe Proposed Services

• Authorities

• Service Availability

• Simple Scenarios

• Alternatives – C-B-P model

SeLeNe – University of Cyprus

Introduction

• Service-based Approach– The Grid: Architecture made up of services– Semantic Grid for eScience– Using Services: Examples

• Tools– JXTA (p2p)– Globus (grid)– Web Services– RMI, CORBA

SeLeNe – University of Cyprus

Proposed Services (I)

• Classification: Core\Appended• Relevance to OGSA and Semantic Grid

Trail Management, Authoring, Collaboration

Caching, Search, Replication

Access,Information, Integration

Registration, Security, Communication

Storage

Application

Fabric

Resource

Connectivity

Collective

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Proposed Services (II)

• Core Services– Information Service

• LO Metadata• Services

– Storage Service• Content (LOs)• Metadata physical files• Indices (known sites)

– Communication Service • Available Protocols (TCP\IP,…)

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Proposed Services (III)

• Appended Services– Registration– Search

• Uses the information Service• Schema heterogeneity issues – Clusters?

– Access• Allow local and remote access to heterogeneous LOs via

a common API

– Caching• Local and Remote• Content, Service and Message caching

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Proposed Services (IV)

• Appended Services– Replication

• File copying and Transferring (Access Serv)• Single Owner• Update Propagation• Object Lookup: logical-to-physical

– Security• On local data• Third party

– Collaboration• Possibly available Services (Blackboards, Message

Boards) managed by high level service

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Proposed Services (V)

• Appended Services– Integration Service

• Transparent integration mechanism

– Authoring• Create and visualize

– Trail Management• Knowledge Layer• The most difficult to design at this point

(requires lower level services)

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Authorities

• Super-peer like• Reliable service provision• Static participation• Provide persistent services including:

Collaboration, Caching, Registration, Integration…

• Roles:– Mediators (handle ontology diversion)– Coordinators (e.g. maintain Collaboration state,

manage Integration process)– Third party (security, pricing)

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Service Availability

• Basic services are made core.

• Reliable sites (authorities) provide popular/demanding services

• Service replication

• Break services to smaller components

• Remote service starting to save resources

• Predictable service shutdown

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Example (I)

A

B

C

D

E

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Example (II)

• ‘C’ Uses Search service • identifies sites ‘A’ and ‘D’• Integration service at site ‘B’ used

user-view• Access service at site ‘A’ • Saved at the local cache• Replication Service at ‘B’: Replicate

locally a part• Information service: new

interconnections/ relationships between LOs.

an individual author creating a new derived LO and itsassociated metadata from other LOs

A Core, Search, Access,

B Core, Collaboration, Registration, Integration, Search, Replication

C Core, Search, Authoring, Cache

D Core, Search

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Alternatives (I)

• Maintain the Service-based focus

• Create sets of services

• “Consumer” services, “Brokering” services and “Producer” services

• Two different Setups presented later

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Alternatives (II)

• Views to the C-B-P architecture

Grid Like Super-Peer like

SeLeNe

Brokers

ProducersConsumers

Producer

Consumer

Broker

Broker

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Alternatives (II)

• Setup 1– Define strict roles to each site

• Producer Services: Repositories• Consumer Services: Client• Brokering Services: Brokers • Analogy to Database Users

Repositories

Brokers

Clients

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Alternatives (III)

• Setup 2– Allow Consumer\Producer services to be co-

located at sites i.e. LOs stored at any site– May require site collaboration– Local Services (more independent)

Brokers

Consumer Producer Consumer\Producer

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Comparison (I)

• Distribution of Services– Pure Grid: “Heavy”, weight on servers– Grid\P2P: more flexible, site of various resources– C-B-P: Somewhere in the Middle

• Dynamic– Pure Grid: Low. Server site must remain up and

be static but highly available– Grid\P2P and C-B-P: highly dynamic but no quality

of service – can be dealt with! – Dynamic nature Vs Availability Trade-offs

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Comparison (II)

• Managerial Ease– Pure Grid and C-B-P: Highly Manageable-

strict service specification– P2P\Grid: Difficult to manage, independent

sites. More supported services (powerful) - autonomy Vs Light but dependent

SeLeNe – University of Cyprus