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Workflow Description for Open Hypermedia
Systems
Sanjay Vivek, David C. De Roure
Department of Electronics and Computer ScienceUniversity of Southampton, UK
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Outline
Brief history of third party link services What is workflow? Web Services and OHS Web Services Flow Language(WSFL) and
workflow concepts Roles in OHS Recursive composition Summary and Discussion
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Simple Open Hypermedia architecture
Link database
documents
Note the direction of this arrow!
Separable hyperstructure
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Documents in native format
Hypermedia Link service
Customised hypermedia documents
Query(before, during or after doc is delivered)
Open Hypermedia as a Link Service
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ProxyDLS
client
Link service
Internet
The ‘Proxy DLS’ is an HTTP proxy that inserts links on-the-fly by querying the link service
Proxy DLS
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resolver
resolver
resolver
resolver
resolverconcurrency
fault tolerance
aggregation
DLS distributed architectureQUERY
Music content-based navigation
Link-enabled Application
LINK
Link ManagerAvailable Links
Interface
FeatureExtractor
FeatureMatching +Retrieval
LinkService
D.L.S.
FeatureAgents
Digital Library
Link Database
Feature Database
Streaming media using RTSP over IPv6
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Overview
Introduce workflow support for OHS Expose these OHS components as Web
Services Enable integration and coordination with
Web Services Flow Language (WSFL)
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What is workflow?
Workflow deals with the management, specification, and execution of operations (business processes) in organizations
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Agent Technology: A Canonical View
Environment
Agent
InteractionsOrganisationalrelationships
Sphere of influenceJennings, CACM
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WSFL and workflow concepts
XML language for the description of Web Services compositions
Essentially a specification to implement a business process model
Uses a workflow engine like the MQSeries Workflow to consume WSFL
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<globalModel name="bookTripNTickets" serviceproviderType="agentType">
<serviceProvider name="travelAgent" serviceProviderType="tio:agentType">
<export> <source portType="tio:tripHandler"
operation="sendItinerary"/> <target portType="tio:tripNTicketHandler"
operation="sendItinerary"/> </export> <export> <source portType="tio:tripHandler"
operation="receiveTripOrder"/> <target portType="tio:tripNTicketHandler"
operation="receiveTripOrder"/> </export> <locator type="..." /> </serviceProvider>
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Web Services and OHS(i)
To simplify the development and integration of distributed hypermedia services over the network
Web services enable you to loosely couple processes
Workflow helps integrate new and existing services
Previous work (Haake) in CSCW context rather than web services
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Web Services and OHS(ii)
An example OHS model consists of the client, a link service, and a linkbase
OHS components are clearly defined and can be described as a Web Service
Workflow helps sequence, coordinate, and manages conversations among Web services
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WSFL and workflow concepts(ii)
Submit QueryCertify Client
TranscodingService
User Profile
Submit QueryWith User Data
Receive Query
Transmit Query
Client Link Service LinkBase
Receive Query
Start
End
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WSFL and workflow concepts(ii) Each box is an activity
and is a WebService Processing logic is
indicated by the directed edges
Control points ensure if certain conditions are met before processing the next activity
Submit QueryCertify Client
TranscodingService
User Profile
Submit QueryWith User Data
Receive Query
Transmit Query
Client Link Service LinkBase
Receive Query
Start
End
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Roles in OHS
Every activity is implemented as a Web Service offered by a Web Service provider
The example OHS Model can be described in WSDL as follows:
<serviceProvider name =”Client” type=”client”/>
<serviceProvider name =”Linkservice” type=”linkservice”/>
<serviceProvider name=”Linkbase” type=”linkbase”/>
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Recursive Composition
Enables service providers to combine services into a single solution
The end user will see the Web Service as a single entity and not as a composite of web services