Title: A Mediated Approach to Semantic Web Services Composition NWG 04 Seminar
1A Mediated Approach to Semantic Web Services
CompositionNWG - 04 Seminar
- Sinuhé Arroyo
- http//www.deri.at/
- Leopold-Franzens Universität Innsbruck
2Contents
- Semantic Web Service Usage Process
- SWS Composition as Mediation
- A Mediated Approach to Composition
- Current Initiatives and Mediation
- SWS composition as mediation in WSMO
3Semantic Web Service Usage process
4Usage 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.
5Usage 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.
6SWS Composition as Mediation
7Mediation
- 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).
8Mediation
- 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.
9Mediation
- Business models Services belonging to different
business models require the appropriate process
mediation in order to permit its cooperation.
10Composition
- 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
11A 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.
12Composition
- 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.
13Composition
14Components
- Components
- Atomic building block for composition
- produces the cooked elements from the raw elements
15Mediation Components for composition
- Selection Mediator
- Coupling Mediator
- Refinement Mediator
- Simple Refiner
- Merger Refiner
- Split Refiner
16Mediation 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.
17Mediation 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.
18Mediation 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
19Mediation Components for composition
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.
20Current Initiatives and Mediation
21Web Services Technologies
22OWL-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
23OWL-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
24Web 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)
25WSMO 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
26SWS Composition as Mediation in WSMO
27Mediation 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.
28Mediators
- 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.
29Mediators
- 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.
30Example 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.
31Example Travel-Booking
32Mediation 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