Enhancing Web Service
Descriptions using WSDL-S
Presented by
Preeda Rajasekaran
LSDIS Lab, University of Georgia
(Under the Direction of John A. Miller)
2
Outline
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Introduction
Adding Semantics to Web Services
WSDL-S
Source Code Annotation
METEOR-S
METEOR-S, SWSDT (Semantic Web Services
Development Tool)
Related Work
Conclusion
Future Work
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Introduction
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Introduction
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Web Service based IT infrastructures becoming
popular
 Industry wide standardization (WSDL, SOAP
etc. )
 XML based technologies which run over Web
servers
 Gartner claims by 2008 60% of IT infrastructure
will be Web service based [http://www.itfacts.biz/index.php?id=P408]
Current state of Web service usage
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Manual application integration (typically internal)
The promise
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Automatic (semi-automatic) application integration on the
fly
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Goals
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(Semi) Automatic Integration
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Current standards like WSDL, UDDI are syntactical
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Semantic heterogeneity in data [Sheth & Larson, 1990] and
functions
Need to provide semantic underpinnings to handle
semantic heterogeneity (ambiguity)
This work
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Deals with adding semantics to Web Service Description
Language (WSDL) by proposing WSDL-S
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What are Web Services ?
* WSDL – Web Service
Description Language
2. WSDL
4. Requested
Service
WSDL
3. Service
Discovery
Query
Service
Requestor
* UDDI – Universal
Description, Discovery
and Integration
UDDI
Service
Registry
* SOAP – Simple Object
Access Protocol
1. WSDL
Interface
5. Service Request
Service
Provider
6. Service Response
WSDL
Web Services Interaction Model
“self-contained,selfdescribing,modular
applications that can be
published, located, and
invoked across the Web”
[IBM Web Service Tutorial]
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What are Semantics?
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Semantics deals with meaning/content.
Helps to express relationship between word
symbols and their intended meaning
A Service represented in many ways may still
have the same context –semantics captures
this.
Enables to ‘understand’ the content.
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How to represent Semantics?
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Representation of semantics via ontologies.
Ontology
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‘ a set of distinct objects resulting from an
analysis of a domain, or microworld’.
Provides a representation of the real world
Ontologies serve as an agreed vocabulary of
terms and their intended meaning.
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OWL- Web Ontology Language
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Standard accepted by W3C
Based on Description Logic
Used to represent the real world
OWL
Description Logics
RDF/RDFS
XML/XSD
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Introduction
Adding Semantics to Web Services
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Semantic Web Services
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Web Services enhanced with the power of semantics
- Semantics
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Semantics in Semantic Web
Service Architecture
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Enhanced UDDI
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Service Provider
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Data structure of UDDI is organized so as to hold
semantic information
Annotated WSDL files – which contain semantic
information about the service
Service Requestor
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Service Templates – Semantically enriched
discovery queries
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Web Services Descriptions
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WSDL provides the interface for the
operations offered by a service.
Service Description Contains
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Operation Name, Input , Output, Exceptions,
Transport and Message protocol, Access Port.
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Semantic Modeling Of An
Operation (in WSDL-S)
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Classification of operation
output = pre ( input ) ? f ( input , state i ): g (
input, state i ) [C-like conditional IF expression]
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State i +1 = h ( input, state i )
assert post ( output, state i+1 ) = 1
f() – output function
g() – exception function
h()- transition function
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Introduction
Adding Semantics to Web Services
WSDL-S
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WSDL-S
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WSDL-S (WSDL with Semantic Annotation)
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Mapping Input and Output Message Parts to Ontology
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Mapping Operations to Ontology
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XML Schema elements used in Input/Output messages do not reflect the semantics of
the data involved in Web Service operation
Use of ontologies or standard vocabulary* provides well defined semantics for
operational data
Service selection involves discovering appropriate WSDL description and locating an
operation to invoke
Operations with same signature could have different functionalities
Ontology or vocabulary* depicting functionality is used for annotation
Additional tags to represent pre-conditions and effects/postconditions of each operation
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Pre-conditions and Post-Conditions are added for each operation
Can be optionally used for service discovery and selection
* RosettaNet Business/Technical dictionary or ebXML Core Component catalog/dictionary
* Current implementation uses vocabularies
The focus of our work is not in developing ontologies for representing functionality/preconditions/effects but to use such
ontologies for semantic annotation
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WSDL 1.1 Meta Model
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WSDL-S 1.1 MetaModel
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WSDL-S 1.1 tags
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“wsdls:concept”
Attribute of operation and part tag.
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“ wsdl:precondition”
Attribute of operation tag. Multiple seperated by ‘&&’.
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“wsdl:postcondition”
Attribute of the operation tag. Multiple seperated by ‘&&’.
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“wsdls:location”
Attribute of service tag.
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“wsdls:domain”
Attribute of service tag.
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WSDL-S 1.1 Code Snippet
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WSDL 2.0
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Current Working Draft
Type information moved outside the standard
Commonly used types : XSD, XMI
This features helps to
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Add OWL as a semantic type (semantic
annotations)
WSDL 2.0 Components
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WSDL-S 2.0 Meta Model
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Introduction
Adding Semantics to Web Services
WSDL-S
Source Code Annotation
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Source Code based Development
of SWS
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Capture the semantics of the service and the
operations
Java 5.0 Meta-Tag Feature
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Incorporate semantics during service
interface design
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JSR 175 & JSR 181
Helps to create service implementation
Similar to javadoc Comments
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Base JSR 181 Tags
MetaTag Name
Description
WebService
Marks a particular Java Implementation
to be a Web Service.
WebMethod
Marks individual methods to be exposed
as Web Service Operations.
WebParam
Used to represent the WSDL message
part element for an operation input.
WebResult
Used to represent the WSDL message
part element for an operation output.
SOAPBinding
Specifies the mapping of the Web Service onto
the SOAP message protocol.
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Semantic Meta-tags
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Extends JSR 181 Tags used to represent
Web Services
Each Tag corresponds to a WSDL element
Semantic Information collected using Java 5
Reflection API.
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Semantic Meta-tags
MetaTag Name
WSDL
Tag
SemanticWebService
(Service Level)
Service
SemanticWebMethod
(Method Level)
Operation
SemanticWebParam
(Method Level)
SemanticWebResult
(Method Level)
Part
Part
Description
Specifies semantics associated with the service
like service- location and service- domain.
Associates semantic concept with Web Method.
Encapsulates Web Method tag. Value of the
‘action’ attribute provides the functional
semantics of the operation.
Associates semantic concept with input
parameter of an operation. Encapsulates
WebParam tag. Value of the ‘element’ attribute
is used to refer to the semantic type that closely
defines the input parameter. The user needs to
ensure that the semantic and data-type match
before annotating.
Associates semantic concept with output of an
operation. Encapsulates WebResult tag.
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Semantic Meta-tags
MetaTag Name
exception
(Method Level)
WSDL
Tag
fault
exceptions
(Method Level)
pre
(Method Level)
Description
Associates semantic concept with
exceptions thrown by methods. This tag
represents multiple exceptions thrown by an
operation.
Collection (Array) of exception tags.
operation
Represents the pre conditions.
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Semantic Meta-tags
MetaTag Name
WSDL
Tag
post
(Method Level)
operation
Constraints
(Method Level)
operation
Collection of pre and post tags.
PortType
(Service Level)
portType
Associates a name with the port Type.
Namespace
(Service Level)
Definitions
Description
Represents the post conditions.
Defines namespaces for the annotations
incorporated.
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Semantic Meta-tags
MetaTag Name
WSDL
Tag
Namespaces
(Service Level)
Binding
(Service Level)
Description
Collection (Array) of namespaces.
Binding
Service
(Service Level)
Service
Port
(Service Level)
port
Used to specify the name associated with
‘SOAPBinding’. Extends SOAPBinding
metatag.
Collection (Array) of related ports.
Defines individual endpoint by specifying a
single address.
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Snippet - Operation Level
Annotations
- Semantic Tags
- JSR 181 Tags
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Snippet – Service Level
Annotations
- Semantic Tags
- JSR 181 Tags
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Introduction
Adding Semantics to Web Services
WSDL-S
Source Code Annotation
METEOR-S
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METEOR-S
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Workflow management for Semantic Web
Services is called METEOR-S (METEOR for
Semantic Web Services)
Uses semantics in the entire life cycle of
Semantic Web Services and Processes
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Semantics in Annotation, Publication, Discovery,
Constraint Driven Composition and Execution of
Web Services
METEOR- Managing End-To-End OpeRations
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METEOR-S
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Comprehensive use of semantics
(Data,Functional,QoS and Execution)
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Functional Semantics
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To represent Service/Operation functionality
Pre/Post conditions
Data Semantics
To represent inputs, output, faults (exceptions).
Integrates and co-exists with current industry tools,
E.g. Eclipse BPWS4J Editor, BPEL4WS Execution
Engine.
Consistent with and builds upon current standards
and recommendations.
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METEOR-S Architecture
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Introduction
Adding Semantics to Web Services
WSDL-S
Source Code Annotation
METEOR-S, SWSDT (Semantic Web
Services Development Tool)
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Semantic Web Services
Development
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Main stages of Semantic Web Service (SWS)
Development
1)Design
3)Implementation
5)Publication
7)Invocation
9)Execution
2)Annotation
4)Deployment
6)Discovery
8)Composition
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METEOR-S SWSDT [Semantic
Web Services Development Tool]
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Developed as an Eclipse Plug-in
Used to incorporate semantic annotations
into Web Services.
Helps to develop
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Annotated Java source Code
Annotated WSDL files (WSDL-S 1.1 & WSDL-S
2.0)
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METEOR-S SWSDT
1
3
2
4
5
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METEOR-S SWSDT
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The different file generations possible using
the tool
Java based
development of
SWS
WSDL based
development of
SWS
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METEOR-S SWSDT Features
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Easy view of WSDL and Java File
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Tree representation
 For Browsing and Editing annotations
Simultaneous view of Ontology when browsing
WSDL/Java files
GUI based incorporation of annotation
Incorporates external modules
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MWSAF – For Automatic Annotation
Publisher – For publishing SWS into Enhanced UDDI
Discovery – Semantic Discovery of Services using heuristic
based subsumption
Deployment and Invocation – GUI tools for deploying and
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invoking SWS
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METEOR-S SWSDT Architecture
METEOR-S Semantic Web Service
Tool
1
2
GUI for
Manual Java/
WSDL file
Annotation
3
MWSAF –For
Automatic
Annotation
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Annotated
Java Source/
WSDL File
Generators
Semantic Publishing
and Semantic
Discovery Engine
Semantically
Enhanced
UDDI Registry
Deployment and
Invocation GUI
5
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
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

Introduction
Adding Semantics to Web Services
WSDL-S
Source Code Annotation
METEOR-S, SWSDT (Semantic Web
Services Development Tool)
Related Work
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Related Work
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OWL-S
DERI Project - WSMO
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Research Project of DERI (Digital Enterprise
Research Institute)
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OWL-S
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OWL-S METEOR-S Comparison
OWL-S
METEOR-S
Service Descriptions
Service Profile + WSDL
WSDL-S
To use/invoke
Service Model + Service
Grounding +WSDL
WSDL-S
Process Model
BPEL (Business Process
Execution Language)
Interaction between
Services
Elements Annotated
I –Inputs
O -Outputs
P –Pre-Conditions
E -Effects
Repository of services
Collection of profile instances/
UDDI
Functionality of the
operation, Input, Output,
Pre-Conditions, PostConditions and Faults
Semantically Enhanced
UDDI
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Semantic Web Services (WSMO)
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WSMO (Web Services Modeling Ontology)
Two parts
 WSML – Semantic Web Service Language based on F-logic
 WSMX – Semantic Web Service Architecture
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Based on WSMF proposed by Bussler and Fensel
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WSMO Supports
 Functional Aspects = (IOPEs) + used mediators
 Non Functional Aspects = performance, reliability, security etc.
 Mediators (components cannot communicate without them)
 Petri nets for execution semantics
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METEOR-S, OWL-S & WSMO
METEOR-S
OWL-S
DERI
Service
Descriptions
WSDL-S
WSDL+
Service Profile
WSMO
Dynamic
Execution
METEOR-S
Dynamic
Processor
Semantic Web
Language Used
OWL
OWL-S Virtual
Machine
OWL
WSMX
[Web Services
Execution
Environment]
WSML
[Web Services
Modeling Language]
(F-logic)
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
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

Introduction
Adding Semantics to Web Services
WSDL-S
Source Code Annotation
METEOR-S, SWSDT (Semantic Web
Services Development Tool)
Related Work
Conclusion
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Conclusion
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Overview
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Shift towards
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Modularization of software components
Automatic integration
Web Services
Requirement of richer service descriptions
Semantics + Web Services = Semantic Web
Services
Representation of semantics in Web Services
Incorporation of semantics into Web Services
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Conclusion
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Representing semantics in Web Services
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WSDL-S
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Source Code Annotations
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Extend WSDL to accommodate semantics
Tags to incorporate semantics were decided and introduced
JSR 181 processor to process the annotations
Incorporating Semantics into Web Services
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METEOR-S SWSDT Eclipse Plug-in
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Developed and released as an open source project.
Available for download,along with installation and user guide at
http://lsdis.cs.uga.edu/projects/METEOR-S/Downloads
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Conclusion
AUTOMATION
SEMANTIC
WEB SERVICES
WEB SERVICES
WE ARE HERE
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


Introduction
Adding Semantics to Web Services
WSDL-S
Source Code Annotation
METEOR-S, SWSDT (Semantic Web Services
Development Tool)
Related Work
Conclusion
Future Work
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Future Work
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Annotation of Complex Types
 Move Annotation to Basic types
Meta-tags to represent Execution Semantics -QoS
Representation of Pre and Post Conditions
WSDL-S 1.1
WSDL-S 2.0
 Complete Generation based on revised WSDL 2.0 Specification
Performance testing of Semantic Web Services
APT for processing annotations
Use of Digestors
 To parse WSDL files
JUnit like test environment for Semantic Web Services
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Questions
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Thank You.
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References
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METEOR
MWSAF - METEOR-S Semantic Web
Service Annotation Framework (MWSAF)
METEOR-S Web Service Composition
Framework (MWSCF)
METEOR-S Web Service Discovery
Infrastructure (MWSDI)
METEOR-S Dynamic Orchestration
Environment (MDOE)
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DEMO of METEOR-S
SWSDT…
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BACK-UP SLIDES
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Service Publication
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Performed by Service Provider
 Discover existing interfaces (services)
to extend
 Create service implementations and
WSDL based definitions
 Test , Deploy and Publish the services, in
Service Registries (e.g.) Enhanced UDDI
Semantics
 Used to capture the behavior of the
published service
 Enables effective discovery by service requestors
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Service Discovery
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Based on Service requestor needs
To find the service providing
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Required operations (methods)
Required signature for static/dynamic binding
Satisfying the requestors constraints such
as QoS, Service locality, etc.
Semantics
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To return relevant services ranked
based on semantic match criteria
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Service Invocation
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Service Invocation
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Performed by Service Requestor after
discovering required services
Invoke a service using
WSDL Specifications
 SOAP Protocol
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Semantics
Apply transformations
when necessary to enable service invocation

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A Plan for Building a SOA –
Web Services
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Requirement #1: Interaction protocols must be standardized.
 WSDL,SOAP, UDDI –standardized
 Need to ensure the widest interoperability among unrelated institutions.
Requirement #2: Make all contracts explicit.
 WSDL makes interface definition explicit
 Explicit contracts define what may be changed in an application without
breaking the interaction.
 It is hard or impossible to make all assumptions explicit, but the more
the better.
Requirement #2 : Standardize contract language(s) and formats.
 Use of XML messages
 Standard metadata is the basis of interoperable contract selection and
execution.
Requirement #3: Allow for points of variability in the contract.
 Use of extensibility elements in WSDL
 Dynamic adaptation on variability points.
 Increases the number of possible interactions supported.
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Requirement #4: Provide native composition models and runtimes.
[Kunal,2004]
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Description Logic

Description Logic is one of the ‘most
important knowledge representation
formalism unifying and giving a logical basis
to the well known traditions of Frame-based
systems, Semantic Networks and KL-ONElike languages, Object-Oriented
representations, Semantic data models, and
Type systems’
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DL and OWL
DL Construct
OWL-DL construct
Atomic concept
(A)
Class (A’)
Universal concept
(the entire world)
(T)
OWL: Thing
Bottom concept (nothing)
()
OWL: Nothing
Atomic negation
()
complementOf (C)
Conjunction
(  )
unionOf (C1 . . .Cn)
Disjunction
(  )
intersectionOf (C1 . . .Cn)
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DL and OWL
DL Construct
Value restriction
( e.g. , , , )
Limited existential quantification
( e.g. , )
OWL Consturcts Ledger:
A’ – Class
C - Description
o – individual name
R - object or abstract property
T – Datatype property
B - DataType
OWL-DL construct
restriction (R
{allValuesFrom(C)}
{someValuesFrom(C)}
{value(o)} [minCardinality(n)]
[maxCardinality(m)] [cardinality(l)])
oneOf(o1 . . . on) ,
restriction (T
{allValuesFrom(D)}
{someValuesFrom(D)}
{value(v)} [minCardinality(n)]
[maxCardinality(m)] [cardinality(l)])
D – Data range
v – data value
l,m,n – non-negative integers
{elements}- can be repeated zero or more times
[elements] -optional
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WSMO - Goals
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A goal specifies the objectives that a client
may have when he consults a web service
E.g. of goals
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Buy a book
Buy a book from Amazon
Buy a book written by X
Mediators can combine or refine goals

E.g. Buy a book from Amazon written by X
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[Verma,2004]
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Semantic Web Services (WSMO)
Two types of mediators

Refiners define a new component as a refinement of an
existing component
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ggMediators: mediators that link two goals. This link
represents the refinement of the source goal into the target
goal.
ooMediators: mediators that import ontologies and resolve
possible representation mismatches between ontologies
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[Verma,2004]
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Semantic Web Services (WSMO)
Two types of mediators

Bridges support reuse by enabling two components
to interact with each other

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wgMediators: mediators that link web service to goals.
They explicitly may state the difference (reduction)
between the two components and map different
vocabularies (through the use of ooMediators).
wwMediators: mediators linking two Web Services.
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[Verma,2004]
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WSMO –Web Service Modeling
Ontology

Represents Semantic Web Services by F-logic

F-logic is used to

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
Describe ontologies
Describe rules and
goals
Uses Mediators to
bring about
inter-operability
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[Verma,2004]