Semantic Web Services

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Semantic Web Services

• Prof. Dr. Heiner Stuckenschmidt
• Universität Mannheim

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Überblick

• Web Services
• Web Service Descriptions
• Semantic Web Services
• Web Service Ontologies
• Learning Web Service Ontologies

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From the Web to Web Services
Semantic
Semantic Web
Annotation
Functionality
Traditional Web
Service Web
Syntactic
Static
Dynamic
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Service Oriented Architecture

• Service oriented architecture provides a standard
  means for interoperability of application
• that operate over the Internet where speed and
  reliability cannot be guaranteed
• whose deployment cannot be managed centrally
• that run on different platforms and vendor
  products
• need to be exposed for use over a network, such
  as the Internet

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Definition Web Service

• A web service is
• a software system
• designed to support interoprable
  machine-to-machine interaction
• over a network.
• A web service has
• An interface
• typically conveyed using HTTP with an XML
  serialization
• described in a machine processable format.

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Web Service Descriptions

• A service description specifies
• The format of massages to communicate with the
  service
• Datatypes used to represent in- and outputs of
  the service
• Transport protocols and serialization to be used
• Service Semantics (not part of the description !)
• the expected behavior of the service in response
  to a message.
• the intended meaning of the input and output data

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Interaction via Web Services

• Requester and Provider become known to each other
  
• Requester and Provider agree on service
  description and semantics
• Service descriptions are realized by the agents
• Requester and provider agents exchange messages,
  thus performing the task

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Requester
Provider
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WSD
WSS
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3
Requester Agent
Provider Agent
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Tasks connected with Web Services

• Web Service Discovery Selection
• Find an airline that can fly me to Marina del
  Rey, CA.
• Web Service Invocation
• Book flight tickets from USAirways to arrive 12th
  Oct.
• Web Service Composition Interoperation
• Arrange taxis, flights and hotel for travel from
  Southampton to Portland, OR, via Marina del Rey,
  CA.
• Web Service Execution Monitoring
• Has the taxi to Gatwick Airport been reserved
  yet?

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Web Service Discovery

• A registry is an authoritative, centrally
  controlled store
• Service providers actively place service
  description in the registry
• The registry owner decides who inserts what
  information
• An index is an automatically created guide to
  information
• Information about available services is collected
  and stored
• Different parties can maintain different indices
• In a P2P setting discovery is done dynamically
• Services know about neighboring services
• Queries by requester agents are forwarded to
  neighbors

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Web Service Technologies

• The general architecture is implemented in W3C
  standards

Base Technologies XML, XML Schema
Descriptions WSDL Web Service Description
Language
Messages SOAP Simple Object Access Protocol
Communication HTTP Hypertext Transfer Protocol
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Web Service Description Language

• A WSDL document is an XML document defining
• Service a collection of related network
  endpoints
• Operations actions supported by the service
• Port Types Sets of operations supported by an
  endpoint
• Binding concrete protocol and data format for a
  port type
• Port a single endpoint in terms of a binding and
  an address
• Types a container for data type definitions
• Messages typed definitions of data being
  exchanged

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WSDL Structure
Service

• portType
• Abstract definition of a service (set of
  operations)
• Multiple bindings per portType
• How to access it
• SOAP, JMS, direct call
• Ports
• Where to access it

Port (e.g. http//host/svc)
Port
Binding (e.g. SOAP)
Binding
Abstract interface
portType
operation(s)
inMesage
outMessage
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An Example Stock Quotes

• The service supports a single operation called
  GetLastTradePrice
• The operation is deployed using the SOAP protocol
  over HTTP.
• The service accepts a ticker symbol of type
  string as input and returns the trade price as a
  float number.

ltservice nameStockQuoteServicegt
ltdocumentationgtAn Example Web Servicelt/documentati
ongt ltport nameStockQuotePort
bindingtnsStockQuoteBindinggt
ltsoapaddress locationhttp//example.com/stockqu
ote/gt lt/portgt lt/servicegt
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Ports and Messages
ltportType nameStockQuotePortTypegt
ltoperation nameGetLastTradePricegt
ltinput messagetnsGetLastTradePriceInput/gt
ltoutput messagetnsGetLastTRadePriceOutput
/gt lt/operationgt lt/portTypegt
ltmessage nameGetLastTradePriceInputgt
ltpart namebody elementxsd1TradePriceRequest
/gt lt/messagegt ltmessage nameGetLastTradePriceOut
putgt ltpart namebody elementxsd1TradePr
ice/gt lt/messagegt
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Type Definitions
lttypesgt ltschema targetNamespacehttp//exampl
e.com/stockquotes.xsd xmlnshttp//www.w3.o
rg/2000/10/XMLSchemagt ltelement
nameTradePriceRequestgt
ltcomplexTypegt ltallgt
ltelement nametickerSymbol
typestringgt lt/allgt
lt/complexTypegt lt/elementgt
ltelement nameTradePricegt
ltcomplexTypegt ltallgt
ltelement nameprice typefloatgt
lt/allgt lt/complexTypegt
lt/elementgt lt/typesgt
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Role of WSDL

• WSDL provides a definition of the programming
  interface of the service
• Ports define physical access points for the
  service
• Port types specify possible operations
• Messages define in- and outputs of operations
• Types define XML format in which in- and outputs
  have to be provided

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Tasks revisited

• Web Service Discovery Selection
• Find an airline that can fly me to Marina del
  Rey, CA.
• Web Service Invocation
• Book flight tickets from USAirways to arrive 12th
  Oct.
• Web Service Composition Interoperation
• Arrange taxis, flights and hotel for travel from
  Southampton to Portland, OR, via Marina del Rey,
  CA.
• Web Service Execution Monitoring
• Has the taxi to Gatwick Airport been reserved
  yet?

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Specifying Service Semantics

• Web Service Discovery requires to search for
  appropriate services based on functionality
  descriptions (Semantics).
• An appropriate Language for representing
  functional descriptions should at least be
• Web friendly (based on URIs and globally
  scalable)
• Unambiguous
• Capable of expressing complex functionality
• Capable of expressing new vocabularies and
  relations between functionalities

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to Semantic Web Services
Semantic
Semantic Web Services
Functionality
Semantic Web
Annotation
Annotation
Functionality
Traditional Web
Service Web
Syntactic
Static
Dynamic
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Requirements for Semantic Descriptions

• For computer programs to successfully interact
• There must be an agreement on the communication
  channel
• There must be an agreement on the form of the
  data
• There must be an agreement on the intended
  meaning of data
• There must be an agreement on the behavior of a
  service

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Semantic Web Service

• Semantic WS - semantically annotated WS to
  automate discovery, composition, execution
• Example

lt rdfIDWS1"gt
ltowlshasInput rdfresource /gt
ltowlshasInput rdfresource
/gt ltowlshasOutput
rdfresource
/gt lt/ gt
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OWL-S A Service Ontology

• OWL-S is an OWL ontology for describing services.
  
• It can be combined with domain ontologies
  describing the meaning of the data processed by a
  service

Service
Service Profile
Service Model
Service Grounding
How to access it data models and communication
What it does functionality and tasks
How it works behavior of the service
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Service vs. Ontology
OWL Ontology
OWL Ontology
Profile Ontology
OWL-S
E_Commerce
Profile
Service
Process
Grounding
Book_Selling
Airline_Ticketing

• Domain Ontology
• Airport
• Flight Itinerary
• confirmation
• Reservation Number

OWL Ontology
Profile-Description BravoAir is an airline
ticketing service Input departure and arrival
airport Output confirmation and flight
itinerary or reservation number
Instance
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A Closer Look at OWL-S
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A Closer Look at OWL-S
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Service Grounding
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Domain Ontology OWL Web Ontology Language
Base Technologies RDF, RDF Schema
Service Semantics OWL-SService Ontology
Descriptions WSDL Web Service Description
Language
Base Technologies XML, XML Schema
Messages SOAP Simple Object Access Protocol
Communication HTTP Hypertext Transfer Protocol
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Beispiel Flugbuchung

• Suche nach möglichen Flügen
• Auswahl eines Fluges

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Beispiel Flugbuchung

• Buchung des ausgewählten Fluges

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Domänen-Ontologie

• Beschreibung der Domäne
• Beschreibung von In- und Output sowie Bedingungen
• Relationen zwischen den entsprechenden Klassen

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Atomare Prozesse

• Erstellung von Prozess Instanzen
• Verbindung zu Input und Output (Klassen)
• Bestimmung der Datentypen

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Grounding

• Abbildung Atomarer Prozesse auf WSDL Ports

• Abbildung von Parametern auf Teile von WSDL
  Messages

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Komplexe Prozesse

• Atomare Prozesse
• Kontrollstruktur
• Parameterübergabe

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Service Profile

• Erstellung eines Profils für den Service
• Profil beinhaltet Input und Output Parameter
• Parameter im Profil müssen Teilmenge der
  eigentlichen Parameter sein

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Semantic Services in myGrid

• Grid middleware to support in silico experiments
  in biology
• Bioinformatics programs are exposed as semantic
  web services
• GOALS
• Support Expert to learn
• From more services
• In less time
• A Better ontology (for SWS descriptions

600 (Services)
550 Concepts But only 125 (23) used for SWS tasks
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Extraction method
Replace or delete sequence sections.
D0. Corpus
word 1 replace replace V i
word 2 or or U 1
lex-mod word 3 delete delete
V 1 lex-dep word 4 sequence sequence
N 5 nn word 5 sections section
N 1 obj
S1. MINIPAR (A)
D1. Tagged Corpus
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Implementation in the GATE Framework
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Quantitative Evaluation

• After Pruning
• Low noise gt high precision
• Many new additions, especially for Methods

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Qualitative Evaluation
I wish I had that before!
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Summary Learning Web Service Ontologies

• Achievements
• Methods for Extracting Ontologies from Software
  Documentation
• Implementation of the Methods in the GATE
  Framework
• Evaluation in realistic scenarios
• Impact
• Reference Application for GATE in the Semantic
  Web Area
• Contribution to the myGrid Project