Web Service Modelling
Ontology (WSMO)
John Domingue
Knowledge Media Institute,
The Open University
Ontolog Semantic Web Service Ontology Standard Panel, October 20th 2005
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WSMO Top Level
Notions
Objectives that a client wants to
achieve by using Web Services
Provide the
formally
specified
terminology
of the
information used
by all other
components
Semantic description
of Web Services:
- Capability
(functional)
- Interfaces
(usage)
Connectors between
components with mediation
facilities for handling
heterogeneities
2
WSMO Top Level
Notions
Objectives that a client wants to
achieve by using Web Services
Provide the
formally
specified
terminology
of the
information used
by all other
components
Semantic description
of Web Services:
- Capability
(functional)
- Interfaces
(usage)
Connectors between
components with mediation
facilities for handling
heterogeneities
3
Capability
Specification
•
•
•
Non functional properties
Imported Ontologies
Used mediators
•
Pre-conditions
What a web service expects in order to be able to
provide its service. They define conditions over the input.
Assumptions
Conditions on the state of the world that has to hold before
the Web Service can be executed
Post-conditions
describes the result of the Web Service in relation to the input,
and conditions on it
Effects
Conditions on the state of the world that hold after execution of
the Web Service (i.e. changes in the state of the world)
•
•
•
– OO Mediator: importing ontologies with mismatch resolution
– WG Mediator: link to a Goal wherefore service is not usable a priori
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WSMO Web Service
Description
- complete item description
- quality aspects
- Web Service Management
- Advertising of Web Service
- Support for WS Discovery
Non-functional Properties
Capability
DC + QoS + Version + financial
functional description
client-service
interaction interface
for consuming WS
- External Visible
Behavior
- Communication
Structure
- ‘Grounding’
Web Service
Implementation
(not of interest in Web
Service Description)
WS
WS
WS
realization of
functionality by
aggregating
other Web Services
- functional
decomposition
- WS composition
Choreography --- Service Interfaces --- Orchestration
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Orchestration
Definition
Flight Request
VTA
provides
if hotel = Ø
flight.arrivaltime = hotel.arrivaltime
Capability
Chor.
Interf.
VTA WS
‘Trip Booking’
if flight = Ø
Hotel Request
flight information
Book Flight
Book Hotel
hotel information
process (control + data flow) of goals
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Runtime Orchestration
Capability
flight request
Flight Request
VTA
provides
avaiable flights
Capability
hotel request
Hotel Request
VTA WS
‘Trip Booking’
Flight WS
Orch.
..
if hotel = Ø
book request
Chor.
Interf.
Interface (Chor.)
1) get request
2) provide offer
3) receive selection
4) send confirmation
avaiable hotels
if flight = Ø
Book Flight
booking confirmation
Interface (Chor.)
1) get request
2) provide offer
3) receive selection
4) send confirmation
book request
booking confirmation
Book Hotel
process (control + data flow) between “states”
+ communication behavior of orchestrating Web Service
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Capability
Hotel WS
Orch.
..
WSMO Top Level
Notions
Objectives that a client wants to
achieve by using Web Services
Provide the
formally
specified
terminology
of the
information used
by all other
components
Semantic description
of Web Services:
- Capability
(functional)
- Interfaces
(usage)
Connectors between
components with mediation
facilities for handling
heterogeneities
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Goals
• Ontological De-coupling of Requester and Provider
• Derived from task / problem solving
methods/domain model
• Structure and reuse of requests
–
–
–
–
–
Search
Diagnose
Classify
Personalise
Book a holiday
• Requests may in principle not be satisfiable
• Ontological relationships & mediators used to link
goals to web services
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Goal Specification
• Non functional properties
• Imported Ontologies
• Used mediators
– OO Mediators: importing ontologies with heterogeneity resolution
– GG Mediator:
• Goal definition by reusing an already existing goal
• allows definition of Goal Ontologies
• Requested Capability
– describes service functionality expected to resolve the objective
– defined as capability description from the requester perspective
• Requested Interface
– describes communication behaviour supported by the requester
for consuming a Web Service (Choreography)
– Restrictions / preferences on orchestrations of acceptable Web
Services
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WSMO Top Level
Notions
Objectives that a client wants to
achieve by using Web Services
Provide the
formally
specified
terminology
of the
information used
by all other
components
Semantic description
of Web Services:
- Capability
(functional)
- Interfaces
(usage)
Connectors between
components with mediation
facilities for handling
heterogeneities
11
Mediation
• Heterogeneity …
– For 1$ on programming, $5 - $9 on integration © IBM, Nelson Mattos
– Mismatches on structural / semantic / conceptual / level
– Assume (nearly) always necessary
• Description of role
– Components that resolve mismatches
– Declarative description of arbitrary web service
• Types of Mediation within Semantic Web Services:
(1) Data: mediate heterogeneous Data Sources
(2) Protocol: mediate heterogeneous Communication
Patterns
(3) Process: mediate heterogeneous Business Processes
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WSMO Mediators
Overview
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Mediator Structure
Source
Component
WSMO Mediator
1 .. n
uses a Mediation Service via
Source
Component
1
Target
Component
- as a Goal
- directly
- optionally incl. Mediation
Mediation
Services
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GG Mediators
• Aim:
– Support specification of Goals by re-using existing Goals
– Allow definition of Goal Ontologies (collection of pre-defined
Goals)
– Terminology mismatches handled by OO Mediators
• Example: Goal Refinement
Source Goal
“Buy a ticket”
GG Mediator
Mediation Service
postcondition:
“aTicket memberof trainticket”
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Target Goal
“Buy a Train Ticket”
Acknowledgements
The WSMO work is funded by the European
Commission under the projects DIP, Knowledge
Web, SEKT, SWWS, and Esperonto; by the UK
EPSRC under the AKT project; by Science
Foundation Ireland under the DERI-Lion
project; and by the Austrian government under
the FIT-IT program.
The WSMO Working Group Chairs are:
Christoph Bussler, John Domingue, and
Dieter Fensel
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Relevant URLs
• WSMO
– http://www.wsmo.org/
• IRS
– http://kmi.open.ac.uk/projects/irs/
• DIP
– http://dip.semanticweb.org/
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