1. Web Service Modeling Ontology (WSMO)
Juan Miguel Gomez
DERI, Galway
18th of March 2004

2. Contents Who am I? Mission of WSMO WSMO- Standard
Comparison OWL-S vs WSMO

3. Who am I? PhD student in DERI
Main research interest. Semantic Web Services conversations, processes and coordination

4. What is DERI? Digital Enterprise Research Institute Two locations:
National University of Ireland, Galway
Leopold Franzens Universität, Innsbruck
Mission statement: “Making the Semantic Web and Semantic Web Services a new infrastructure for eCommerce and eWork”

5. Mission of DERI DERI International DERI Galway DERI Innsbruck
Institute Level
DERI Galway
DERI Innsbruck
Centre Level
Knowledge Web
DIP
SEKT
SWWS
ONTOWEB
Esperonto
h – Techsight
COG
Austrian projects
University
ASG
DERI – Lion
DIP
ASG
Knowledge Web
SWWS
University
Project + Cluster
Level

6. Mission of WSMO
Providing a standard for describing semantic web services.
Stands for the Web Service Modeling Ontology
WSMO is derived from the Web Services Modelling Framework (WSMF)
WSMO has an execution platform called WSMX
WSMO working group:

7. WSMO Modular approach WSMO-Lite: Simple model
WSMO- Standard: Core model
WSMO-Full: Business model
… and WSMX

8. WSMX- Execution model
WSMX provides an execution model for running future implementations of WSMO
Message
Ontology
Interface
Invocation
Mediation
System

9. WSMO- Standard

10. WSMO
This document presents an ontology called Web Service Modeling Ontology (WSMO) for describing various aspects related to Semantic Web Service.
Having the Web Service Modeling Framework (WSMF) as a starting point, it refines this framework and develops a formal ontology and a formal language.

11. WSMO Two complementary principles: Maximal decoupling complemented by
scalable mediation service

12. WSMO

13. WSMO - Ontologies Non functional properties Used mediators
Imported ontologies allow a modular approach for ontology design. By importing other ontologies, one can make use of concepts and relations defined elsewhere. Nevertheless, when importing an arbitrary ontology, most likely some steps for aligning, merging and transforming imported ontologies have to be performed. For this reason and in line with the basic design principles underlying the WSMF, we use ontology mediators (ooMediators) for importing ontologies.
Concept definitions
The set of concepts that belong to the represented ontology.
Relation definitions
The set of relations that belong to the represented ontology.
Axioms
The set of axioms that belong to the represented ontology.
Instances
The set of instances that belong to the represented ontology.

14. WSMO - Goals Non functional properties Used mediators Post-conditions
By importing ontologies, a goal can make use of concepts and relations defined elsewhere. A goal can import ontologies using ontology mediators (ooMediators). A goal may be defined by reusing an already existing goal or by combining existing goals. This is achieved by using goal mediators (ggMediators).
Post-conditions
Post-conditions in WSMO describe what a web service returns in response to its input. They define the relation between the inputs and the outputs.
Effects
Effects describe the state of the world after the execution of the service.

15. WSMO - Mediators We distinguish between four different mediators:
ggMediators: mediators that link two goals.
ooMediators: mediators that import ontologies and resolve possible representation mismatches among all imported ontologies.
wgMediators: mediators that link web service to goals, i.e. they explicitly state the difference (reduction) between the two components and map different vocabularies.
wwMediators: mediators linking two Web Services.

16. WSMO Del 2 - Mediators

17. WSMO- Mediators Non functional properties Source component
The source component defines one of the two logically connected entities.
Target component
The target component defines one of the two logically connected entities.
Mediation Service
The mediation service points to a goal that declarative describes the mapping or to a wwMediator that links to a web service that actually implements the mapping.
Reduction
A reduction only exists in a wwMediator or a ggMediator. It describes in a logical formula the differences between the functionality described in the goal and the one of the web service (if any) or another goal.

18. WSMO– Web Service Capability Interfaces Groundings
A capability defines the web service by means of its functionality .
Interfaces
An interface extends the description of the capability to a higher level of complexity.
Groundings
A grounding specifies how to access the service. It has mainly to do with protocol and message formats, serialization, transport and addressing. The grounding is a mapping from the abstract specification to a concrete specification of the elements that describe a service, which are required for interacting with the service.

19. WSMO– Capability Non functional properties Used mediators
By importing ontologies, a capability can make use of concepts and relations defined elsewhere. A capability can import ontologies using ontology mediators (ooMediators). A capability can be linked to a goal using a wgMediator.
Pre-conditions
Pre-conditions in WSMO describe what a web service expects for enabling it to provide its service. They define conditions over the input.
Post-conditions
Post-conditions in WSMO describe what a web service returns in response to its input. They define the relation between the input and the output.
Assumptions
Assumptions are similar to pre-conditions, however, also reference aspects of the state of the world beyond the actual input.
Effects
Effects describe the state of the world after the execution of the service.

20. WSMO– Interfaces Distinction between choreography and orchestration
Non functional parameters
Errors
Compensation
When an invoked service fails (i.e. an error code is returned), the service that invoked it may implement a strategy for compensation. The compensation in fact represents either a wwMediator or a goal.
Message exchange
A message exchange pattern describes the temporal and causal relationships, if any, of multiple messages exchanged.
Distinction between choreography and orchestration

21. WSMO– Language
F-Logic combines the advantages of conceptual high-level approaches typical for frame-based language and the expressiveness, the compact syntax, and the well defined semantics from logics.
it provides a standard model theory
it is a full first order logic language
it provides second order syntax while staying in the first order logic semantics
it has a minimal model semantics
implemented inference engines are already available.

22. OWL-S vs. WSMO Comparison aspect WSMO-Standard v0.1 OWL-S 1.0 Purpose
Clear goal, specific application domains
Too wide, not clear
Principles
Explicit conceptual work and well-established principles
Not explicit, only specifies set of tasks to be solved
Coupling
Loose coupling, independent definition of description elements
Tight coupling in several aspects
Extensibility
Extensible in every direction
Limited extensibility, only through OWL subclassing
Implementation & business layer
Will be clearly separated in WSMO-Full
Messed up e.g. use of the Resource concept
Registry
Not dictated
Requester needs & service capabilities
Two different points of view, modeled independently and linked via wgMediators
Not separated, unified view in the service profile

23. Functionality description Non-functional properties
Comparison aspect
WSMO-Standard v0.1
OWL-S 1.0
Functionality description
Explicit and complete description
Incomplete
Non-functional properties
Pre-defined properties. Flexible extension but not explicit mechanism
Few pre-defined properties. Explicit extension mechanism but improvable flexibility
Orchestration
Supports static and dynamic composition, but under-defined
Limited dynamic composition
Grounding
Multiple groundings, not pre-defined grounding
Multiple groundings, WSDL pre-defined grounding
Mediation
Scalable mediation between loosely coupled elements
No mediation
Layering
3-layers (WSMO-Lite, WSMO-Standard, WSMO-Full) covering different complexity levels of the domain
No layering (layering inherited from OWL, does not reflect complexity of the application domain)
Languages
F-Logic for logical expressions. Detailed justification for the choice. Ontology language not imposed
Language for conditions not defined. OWL is used with no justification

24. Muito Obrigado!!!