Enhancing Web Service Descriptions using WSDL-S

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Enhancing Web Service Descriptions using WSDL-S
Presented by Preeda Rajasekaran LSDIS Lab,
University of Georgia (Under the Direction of
John A. Miller)
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Outline

• 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

• 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?idP408
• Current state of Web service usage
• Manual application integration (typically
  internal)
• The promise
• Automatic (semi-automatic) application
  integration on the fly

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Goals

• (Semi) Automatic Integration
• Semantic heterogeneity in data Sheth Larson,
  1990 and functions
• Current standards like WSDL, UDDI are syntactical
• Need to provide semantic underpinnings to handle
  semantic heterogeneity (ambiguity)
• This work
• 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
UDDI Universal Description, Discovery and
Integration SOAP Simple Object Access
Protocol
UDDI
Service Registry
2. WSDL

• 4. Requested Service WSDL

3. Service Discovery Query
1. WSDL Interface
self-contained,self-describing,modular
applications that can be published, located, and
invoked across the Web IBM Web Service Tutorial
Service Requestor
5. Service Request
Service Provider
6. Service Response
WSDL
Web Services Interaction Model
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What are Semantics?

• 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?

• Representation of semantics via ontologies.
• Ontology
• 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

• 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

• Web Services enhanced with the power of semantics
  

- Semantics
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Semantics in Semantic Web Service Architecture

• Enhanced UDDI
• Data structure of UDDI is organized so as to hold
  semantic information
• Service Provider
• Annotated WSDL files which contain semantic
  information about the service
• Service Requestor
• Service Templates Semantically enriched
  discovery queries

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Web Services Descriptions

• WSDL provides the interface for the operations
  offered by a service.
• Service Description Contains
• Operation Name, Input , Output, Exceptions,
  Transport and Message protocol, Access Port.

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Semantic Modeling Of An Operation (in WSDL-S)

• Classification of operation
• output pre ( input ) ? f ( input , state i )
  g ( input, state i ) C-like conditional IF
  expression
• State i 1 h ( input, state i )
• assert post ( output, state i1 ) 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

• WSDL-S (WSDL with Semantic Annotation)
• Mapping Input and Output Message Parts to
  Ontology
• 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
• Mapping Operations to Ontology
• 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/post-conditions of each operation
• 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

• wsdlsconcept
• Attribute of operation and part tag.
• wsdlprecondition
• Attribute of operation tag. Multiple seperated
  by .
• wsdlpostcondition
• Attribute of the operation tag. Multiple
  seperated by .
• wsdlslocation
• Attribute of service tag.
• wsdlsdomain
• Attribute of service tag.

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WSDL-S 1.1 Code Snippet

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WSDL 2.0

• Current Working Draft
• Type information moved outside the standard
• Commonly used types XSD, XMI
• This features helps to
• 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

• Capture the semantics of the service and the
  operations
• Java 5.0 Meta-Tag Feature
• JSR 175 JSR 181
• Incorporate semantics during service interface
  design
• Helps to create service implementation
• Similar to javadoc Comments

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Base JSR 181 Tags
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Semantic Meta-tags

• 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
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Semantic Meta-tags
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Semantic Meta-tags
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Semantic Meta-tags
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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

• 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
• 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

• Comprehensive use of semantics (Data,Functional,Qo
  S and Execution)
• Functional Semantics
• 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

• Main stages of Semantic Web Service (SWS)
  Development
• 1)Design 2)Annotation
• 3)Implementation 4)Deployment
• 5)Publication 6)Discovery
• 7)Invocation 8)Composition
• 9)Execution

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METEOR-S SWSDT Semantic Web Services Development
Tool

• Developed as an Eclipse Plug-in
• Used to incorporate semantic annotations into Web
  Services.
• Helps to develop
• 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

• 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

• Easy view of WSDL and Java File
• Tree representation
• For Browsing and Editing annotations
• Simultaneous view of Ontology when browsing
  WSDL/Java files
• GUI based incorporation of annotation
• Incorporates external modules
• 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 invoking SWS

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METEOR-S SWSDT Architecture
METEOR-S Semantic Web Service Tool
1
2
Annotated Java Source/ WSDL File Generators
GUI for Manual Java/ WSDL file Annotation
MWSAF For Automatic Annotation
Semantic Publishing and Semantic Discovery Engine
Deployment and Invocation GUI
3
4
5
Semantically Enhanced UDDI Registry
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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

• OWL-S
• DERI Project - WSMO
• Research Project of DERI (Digital Enterprise
  Research Institute)

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OWL-S
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OWL-S METEOR-S Comparison
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Semantic Web Services (WSMO)

• WSMO (Web Services Modeling Ontology)
• Two parts
• WSML Semantic Web Service Language based on
  F-logic
• WSMX Semantic Web Service Architecture
• Based on WSMF proposed by Bussler and Fensel
• 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
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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

• Overview
• Shift towards
• 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

• Representing semantics in Web Services
• WSDL-S
• Extend WSDL to accommodate semantics
• Source Code Annotations
• Tags to incorporate semantics were decided and
  introduced
• JSR 181 processor to process the annotations
• Incorporating Semantics into Web Services
• METEOR-S SWSDT Eclipse Plug-in
• 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

• 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

• 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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METEOR-S SWSDT Packages and Tools used

? Version 1.2 is currently used due to its
compatibility with uddi4j, we will be upgrading
to the latest version of JWSDP in our future
work.
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Service Publication

• 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

• Based on Service requestor needs
• To find the service providing
• Required operations (methods)
• Required signature for static/dynamic binding
• Satisfying the requestors constraints such
• as QoS, Service locality, etc.
• Semantics
• To return relevant services ranked
• based on semantic match criteria

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Service Invocation

• Service Invocation
• Performed by Service Requestor after discovering
  required services
• Invoke a service using
• WSDL Specifications
• SOAP Protocol
• Semantics
• Apply transformations
• when necessary to enable service invocation

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WSDL-S 2.0 Tags

•  
• action
• Attribute is added to operation tag.
• pre and post
• Tags are added as children of the operation tag.
• element
• The use of OWL and XMI types is proposed for the
  values of this attribute.
• exception
• Tag is added as a child of the operation tag.

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WSDL-S 2.0 Snippet
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A Plan for Building a SOA Web Services

• 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.
• 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-ONE-like languages,
  Object-Oriented representations, Semantic data
  models, and Type systems

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DL and OWL
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DL and OWL
OWL Consturcts Ledger A Class D Data
range C - Description v data value o
individual name l,m,n non-negative integers R
- object or abstract property elements-
can be repeated zero or more times T Datatype
property elements -optional B - DataType
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QoS in METEOR-S
QoS
QoS Model
Design
QoS Estimates for Tasks/Web services
QoS Estimates for Transitions
SWR algorithm
Stochastic Process
QoS Computation
Enact
Log
Simulation
Cardoso,2004
72
Web process QoS computation
QoS
Design time Runtime
Linear programming
Price
Security
Simulation
Duration
Time
Petri-nets analysis
Repudiation
Cost
Graph Reduction Techniques
Reliability
Fidelity
Availability
Reliability
Critical Path Algorithm
Cardoso,2004
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DAML-SOntologies

• DAML-S defines ontologies for the construction of
  service models
• Service Profiles
• Process Models
• Service Grounding

Verma,2004
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WSMO - Goals

• A goal specifies the objectives that a client may
  have when he consults a web service
• E.g. of goals
• 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

Verma,2004
75
Semantic Web Services (WSMO)

• Two types of mediators
• Refiners define a new component as a refinement
  of an existing component
• 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

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
• 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.

Verma,2004
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WSMO Web Service Modeling Ontology

• Represents Semantic Web Services by F-logic
• F-logic is used to
• Describe ontologies
• Describe rules and
• goals
• Uses Mediators to
• bring about
• inter-operability

Verma,2004