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A Mediated Approach to Semantic Web Services Composition NWG 04 Seminar

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Arrange services in a particular order also based on its capabilities (composition) ... Task : Book hotel, airline and rent a car from 12nd to 19th, in Innsbruck. ... – PowerPoint PPT presentation

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Title: A Mediated Approach to Semantic Web Services Composition NWG 04 Seminar


1
A Mediated Approach to Semantic Web Services
CompositionNWG - 04 Seminar
  • SinuhĂ© Arroyo
  • http//www.deri.at/
  • Leopold-Franzens Universität Innsbruck

2
Contents
  • Semantic Web Service Usage Process
  • SWS Composition as Mediation
  • A Mediated Approach to Composition
  • Current Initiatives and Mediation
  • SWS composition as mediation in WSMO

3
Semantic Web Service Usage process
4
Usage Process
  • Discovery Location of Services that abides to
    the service requester specification for a
    concrete task .
  • Composition Assembly of Services based on its
    functional specifications in order to achieve a
    given task and provide a higher order of
    functionality.
  • Mediation Arbitration of interacting Services
    in terms of domain knowledge used to describe the
    Services, protocol used in the communication,
    data exchanged in the interaction (types used,
    and meaning of the information) and business
    models of the different parties.

5
Usage Process
  • Execution Invocation of a concrete set of
    services, arranged in a particular way following
    programmatic conventions that realizes a given
    task.
  • Monitoring Supervision of the correct execution
    of services and dealing with exceptions thrown by
    composed services or the composition workflow
    itself.
  • Compensation Replacement of Services by
    equivalent ones, which solely or in combination
    can realize the same functionality as the
    replaced one, in case of failure while execution.

6
SWS Composition as Mediation
7
Mediation
  • It permits to align the different vocabularies
    used to describe the different aspect of Services
    in regard to some domain knowledge
  • Therefore match the capabilities of the Service
    with the requirements of the (sub)task
    (discovery)
  • Arrange services in a particular order also based
    on its capabilities (composition).

8
Mediation
  • Once all the required services to solve a task
    are place together following some programmatic
    conventions (functional point of view),
    interacting Services need to be aligned in terms
    of the
  • Protocol used Different parties might use
    different message exchange patterns and protocols
    which need to be mediated in order enable
    communication.
  • Types and meaning of the exchanged information
    Depending on the business model for which the
    services are deployed, different data types and
    domain knowledge might be used to encapsulate
    data and its meaning, which requires mediation to
    allow interoperation.

9
Mediation
  • Business models Services belonging to different
    business models require the appropriate process
    mediation in order to permit its cooperation.

10
Composition
  • Essentially composition can be envisioned as the
    overcoming of functional interoperation the
    different mismatches that occur among services
  • Protocol
  • Business Models
  • Types and meaning of the exchange information
  • The approach presented in the coming slides
    focuses on the latest

11
A Mediated approach to Composition
Note The work presented in this section was
carried by Han Sung-Kook. Currently we are
working in a paper that puts together all this
ideas.
12
Composition
  • High-level, generic tasks
  • Composition
  • The composition is to produce or
  • generate a solution in the form of
  • functional components or products
  • by means of integrating, mixing or
  • connecting components according to
  • their interpretabilities.

13
Composition
14
Components
  • Components
  • Atomic building block for composition
  • produces the cooked elements from the raw elements

15
Mediation Components for composition
  • Selection Mediator
  • Coupling Mediator
  • Refinement Mediator
  • Simple Refiner
  • Merger Refiner
  • Split Refiner

16
Mediation Components for composition
  • Selection Mediator component SM
  • Mediation to add or eliminate some elements
  • Components to strengthen or weaken the
    capabilities of composed component
  • Example Some one wants to compose coffee with
    milk, not caffeine.

17
Mediation Components for composition
  • Coupling Mediator component CM
  • Simply couple two different structures of
    components
  • A kind of buffer or glue component
  • No functionalities except coupling two different
    components. But, we can define its
    functionalities later.
  • Example Some one want to connect a scanner to
    computer.

where xi ( i 1, n) are the cooked element of
Ci and yj ( j 1, m) are the raw elements of
Cj.
18
Mediation Components for Composition
  • Refinement Mediator component RM
  • Mediator with semantic capabilities
  • Ontological mapping to match types or names of
    elements
  • Semantically merge or split elements

19
Mediation Components for composition
  • Simple Refiner

The names and types of elements xi are converted
into yi.
Merge Refiner
The value of element ym is consisted of xi, xj
and xk. The element ym defines its name and type.
Split Refiner
The value of xi is splitted into ym and yn. The
elements ym and yn define their name and type.
20
Current Initiatives and Mediation
21
Web Services Technologies
22
OWL-S (DARPA Agent Markup Language for Services)
  • OWL-S Ontology that allows the definition of
    knowledge to state what the service requires,
    what provides, how does it do it.
  • Enables advertise and subsequently discover Web
    services.
  • DAML-S refers to the ontology built upon
    DAMlOIL, while OWL-S refers to the one built
    upon OWL.

Adapted from Chandrasekarans
23
OWL-S (DARPA Agent Markup Language for Services)
  • Service Profile High-level description of the
    service that states its intended purpose
  • Service Description
  • Functional Behavior
  • Functional Attributes
  • Service Model Permits the description of the
    functionalities of a service as a process,
    detailing control and data flow structures.
  • Process Ontology (Atomic, Simple and Composite)
  • Process Control Ontology
  • Service Grounding Specifies details regarding
    how to invoke the service, (protocol, messages
    format, serialization, transport and addressing

Adapted from Chandrasekarans
24
Web Service Modelling Ontology
  • WSMO is a conceptual model for the description
    Semantic Web Services
  • Grounded on the Web Service Modeling Framework
    (WSMF)
  • It represents the backbone for the development
    of
  • Web Service Modelling Language (WSML)
  • Web Service Modelling Execution Environment (WSMX)

25
WSMO Elements
Specify objectives that a client may have when
consulting a Web Service
Functional part that must be semantically
described in order to allow its semi-automated
use
Provide the formal semantics to the information
used by all other components
  • Used as connectors provide
  • interoperability facilities among
  • the rest of components

26
SWS Composition as Mediation in WSMO
27
Mediation in WSMO and OWL- S
  • WSM(O/L/X) supports scalable mediation based on
    mediators
  • OOMediators to link 2 ontologies
  • GGMediators to link 2 goals
  • WWMediators to link 2 Web Services
  • WGMediators to link a Web Service and a Goal, or
    more precisely, to link the Capability of a Web
    Service and a Goal.
  • OWL-S does not specify any particular form of
    mediation.

28
Mediators
  • Used as connectors, provide interoperability
  • facilities among the rest of components.
  • Non functional properties
  • Source component
  • Defines one of the two logically connected
    entities.
  • Target component
  • Defines one of the two logically connected
    entities.

29
Mediators
  • Mediation Service
  • Points to
  • a goal that declarative describes the mapping or
  • a wwMediator that links to a web service that
    implements the mapping.
  • Reduction It describes in a logical formula the
    differences between the
  • functionality described in the goal and the
    functionality of the web service (if any) or
    another goal. A reduction only exists in a
    wgMediator or a ggMediator.

30
Example Travel-Booking
  • Task Book hotel, airline and rent a car from
    12nd to 19th, in Innsbruck.
  • simply compose different types of services
  • not consider compensation.
  • Composition using Coupling mediator
  • A coupling mediator can be used for the
    composition of unrelated services. But, actually,
    it is a virtual component to compose unrelated
    services. We can omit coupling mediator in
    composite document if not necessary.

31
Example Travel-Booking
32
Mediation in WSMO
  • Mediation Service
  • a wwMediator that links to a web service that
    implements the mapping.
  • The whole mediation process can be implemented as
    a Web Service which will be implementing the
    maping.

33
  • lt/Thx!!!gt
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