Semantic Web and Exam Preparation - STI Innsbruck...• Semantic Web Services are a layer on top of existing Web service technologies and do not aim to replace them • Provide a formal

1 © Copyright @2009 Dieter Fensel and Mick Kerrigan

Intelligent Systems

Semantic Web and Exam Preparation

2

Where are we?

# Title 1 Introduction

2 Propositional Logic

3 Predicate Logic

4 Theorem Proving, Description Logics and Logic Programming

5 Search Methods

6 CommonKADS

7 Problem Solving Methods

8 Planning

9 Agents

10 Rule Learning

11 Inductive Logic Programming

12 Formal Concept Analysis

13 Neural Networks

14 Semantic Web and Exam Preparation

3

Agenda

•  Semantic Web - Data •  Motivation •  Technical Solution: URI, RDF, RDFS, OWL, SPARQL •  Illustration by Larger Examples: KIM Browser Plugin, Disco Hyperdata Browser •  Extensions: Linked Open Data

•  Semantic Web – Processes •  Motivation •  Technical Solution: Semantic Web Services, WSMO, WSML, SEE, WSMX •  Illustration by Larger Examples: SWS Challenge, Virtual Travel Agency

•  Extensions: WSMX at work

•  Conclusions

3

4

SEMANTIC WEB - DATA

4

5

MOTIVATION

5

6

Motivation

•  If the Web is about the global networking of data through URL, HTML, and HTTP…

•  … the Semantic Web is about the global networking of knowledge through URI, RDF, and SPARQL

•  This knowledge can be an annotation of Web data (this picture depicts Innsbruck) or just for knowledge‘s sake (Innsbruck is a city in Austria)

•  Structured data: –  is a key towards Artificial Intelligence –  is background knowledge –  enables formal reasoning

6

7

TECHNICAL SOLUTIONS

7

8

Uniform Resource Identifier

Taken from http://www.w3.org/TR/webarch/

9

•  URIs are used to identify resources, not just things that exists on the Web, e.g. Dieter Fensel, University of Innsbruck

•  RDF is used to make statements about resources in the form of triples

<entity, property, value>

•  Results in the creation of a labeled directed graph

ex:john ex:bill ex:father-of

ex:bill ex:tom ex:father-of

9

RDF

10

RDFS

•  RDFS is a language for defining RDF types •  Define Classes

–  #Student is a class •  Relationships between classes

–  #Student is a sub-class of #Person •  Properties of classes

–  #Person has a property hasName –  hasName has a domain of Person and a range of a string literal –  Can define relationship between properties with rdfs:subPropertyOf

ex:john ex:student rdf:type

“John Smith”

ex:hasName

10

11

RDFS Example

11

12

OWL

•  The limitation of RDFS is that it only allows binary relations

•  OWL provides an ontology language, that is a more expressive Vocabulary Definition Language for use with RDF

–  Class membership –  Equivalance of classes –  Consistency –  Classification

•  OWL is layered into languages of different expressiveness –  OWL Lite: Classification Hierarchies, Simple Constraints –  OWL DL: Maximal expressiveness while maintaining tractability –  OWL Full: Very high expressiveness, loses tractability, all syntactic freedom of RDF

•  More expressive means harder to reason with

12

13

SPARQL

•  SPARQL is an RDF Query Language •  Uses a SQL-like syntax

•  Example: Find the names of all the Students

PREFIX ex <http://www.example.org/> PREFIX rdfs <http://www.w3.org/1999/02/22-rdf-syntax-ns#>

SELECT ?name FROM <http://www.uibk.ac.at/students> WHERE{

?x rdfs:type ex:student. ?x ex:hasName ?name.

}

?name

John Smith

Tom Johnson

Bill Thompson

13

14

ILLUSTRATION BY LARGER EXAMPLES

14

15

Annotated Content

•  KIM Browser Plugin Web content is annotated using ontologies Content can be searched and browsed intelligently

Select one or more concepts from the ontology… … send the currently loaded web page to the Annotation Server

Illustration 1 – KIM Browser Plugin

15

16

Dereferencable URI

Disco Hyperdata Browser navigating the Semantic Web as an unbound set of data sources

Illustration 2 – Disco Hyperdata Browser

16

17

EXTENSIONS

17

18

Extensions: Linked Open Data

•  Linked Data is a method for exposing and sharing connected data via dereferenceable URI’s on the Web

–  Use URIs to identify things that you expose to the Web as resources –  Use HTTP URIs so that people can locate and look up (dereference) these things –  Provide useful information about the resource when its URI is dereferenced –  Include links to other, related URIs in the exposed data as a means of improving

information discovery on the Web

•  Linked Open Data is an initiative to interlink open data sources –  Open: Publicly available data sets that are accessible to everyone –  Interlinked: Datasets have references to one another allowing them to be used

together

18

19

Extensions: Linked Open Data

19

20

Extensions: Linked Open Data - FOAF

•  Friend Of A Friend (FOAF) provides a way to create machine-readable pages about:

–  People –  The links between them –  The things they do and create

•  Anyone can publish a FOAF file on the web about themselves and this data becomes part of the Web of Data

•  FOAF is connected to many other data sets, including –  Data sets describing music and musicians (Audio Scrobbler, MusicBrainz) –  Data sets describing photographs and who took them (Flickr) –  Data sets describing places and their relationship (GeoNames)

<foaf:Person> <foaf:name>Dieter Fensel</foaf:name> <foaf:homepage rdf:resource="http://www.fensel.com"/>

</foaf:Person>

20

21

Extensions: Linked Open Data - GeoNames

•  The GeoNames Ontology makes it possible to add geospatial semantic information to the Web of Data

•  We can utilize GeoNames location within the FOAF profile

•  GeoNames is also linked to more datasets –  US Census Data –  Movie Database (Linked MDB) –  Extracted data from Wikipedia (DBpedia)

<foaf:Person> <foaf:name>Dieter Fensel</foaf:name> <foaf:homepage rdf:resource="http://www.fensel.com"/> <foaf:based_near ” http://ws.geonames.org/rdf?geonameId=2775220"/>

</foaf:Person>

21

22

Extensions: Linked Open Data - DBpedia

•  DBpedia is a community effort to extract structured information from Wikipedia and to make this information available on the Web

•  As our FOAF profile has been linked to GeoNames, and GeoNames is linked to DBpedia, we can ask some interesting queries over the Web of Data

–  What is the population of the city in which Dieter Fensel lives? => 117916 people

–  At which elevation does Dieter Fensel live? => 574m

–  Who is the mayor of the city in which Dieter Fensel lives => Hilde Zach

22

23

SEMANTIC WEB - PROCESSES

23

24

MOTIVATION

24

25

Motivation

•  The Web is moving from static data to dynamic functionality –  Web services: a piece of software available over the Internet,

using standardized XML messaging systems over the SOAP protocol

–  Mashups: The compounding of two or more pieces of web functionality to create powerful web applications

–  Significant growth of Web APIs •  1.100 Web APIs on ProgrammableWeb.com (including SOAP and REST APIs) •  3.700 Mashups on ProgrammableWeb.com (combining Web APIs from one or

more sources

•  Examples: –  Amazon Web Services –  iGoogle –  Yahoo Pipes –  RSS Feeds 25

25

26 26

Motivation

27

•  Web services and mashups are limited by their syntactic nature

•  As the amount of services on the Web increases it will be harder to find Web services in order to use them in mashups

•  The current amount of human effort required to build applications is not sustainable at a Web scale

Motivation

27

28

TECHNICAL SOLUTIONS

28

29

Semantic Web Services

•  Brings the benefits of Semantics to the executable part of the Web –  Ontologies as data model –  Unambiguous definition of service functionality and external interface

•  Reduce human effort in integrating services in SOA –  Many tasks in the process of using Web services can be automated

•  Improve dynamism –  New services available for use as they appear –  Service Producers and Consumers don’t need to know of each others existence

•  Improve stability –  Service interfaces are not tightly integrated so even less impact from changes –  Services can be easily replaced if they are no longer available –  Failover possibilities are limited only by the number of available services

29

30

Semantic Web Services

•  Semantic Web Services are a layer on top of existing Web service technologies and do not aim to replace them

•  Provide a formal description of services, while still being compliant with existing and emerging technologies

•  Distinguish between a Web service (computational entity) and a service (value provided by invocation)

•  Make Web services easier to: –  Find –  Compare –  Compose –  Invoke

30

31

Conceptual Model for SWS

Formal Language for WSMO

Ontology & Rule Language for the Semantic Web

Technical Overview

31

Execution Environment

For SWS

32

Strict Decoupling of Modeling Elements

Centrality of Mediation

Ontological Role Separation

Description versus Implementation

WSMO Ontology-Based

Web Service versus Service

WSMO – Design Principles

32

33

WSMO – Conceptual Model

Objectives that a client wants to achieve by using Web Services

Formally specified terminology used by all other components

Semantic description of Web Services •  Capability (functional)‏ •  Interfaces (usage)

Connectors between components with mediation facilities for handling heterogeneities

33

34

WSML – Language Family

WSML -‐ Core

WSML -‐ DL

WSML -‐ Full

WSML -‐ Flight

WSML -‐ Rule

f

with

without

34

Exp

ress

ivity

35

Semantic Execution Environment

35

Seman(c Execu(on Environment

Discovery Ranking SelecSon

ComposiSon Data MediaSon Process MediaSon

Process ExecuSon

LiVing & Lowering

base

broker verScal

Mon

itoring

Reasoning Storage

36

Semantic Execution Environment - WSMX

36

37

ILLUSTRATION BY LARGER EXAMPLES

37

38

•  Blue company has discovered Moon company on the Web •  Blue company wishes to communicate with Moon company

•  Broker required to resolve data and process interoperability issues

Purchase Order

Purchase Order Confirmation

id

cid

openOrder

addItem*

closeOrder

Blue Company can only send POs and

receive PO Confirmations

Allows the opening of a PO, the specification of the items

to be purchased and the closing of the PO

Receives a customer id and returns a full

customer description Illustration 1: SWS Challenge

38

39

Rail Services

Flight Services

Hotel Services

Car Hire Services

Illustration 2: Virtual Travel Agency

39

40

EXTENSIONS

40

41

Extensions: WSMX At Work

41

42


Request to discover Web services.

42

43


Goal expressed in WSML is sent to WSMX System Interface

43

44


Com. M. implements the interface to receive WSML goals

44

45


Com. M. informs Core that Goal has been received

45

46


Chor. wrapper picks up event for Chor. component

46

47


New choreography Instance is created

47

48


Core is notified that choreography instance has been created.

48

49


WSML goal is parsed to internal format.

49

50


Discovery is invoked

for parsed goal.

50

51


Discovery may requires ontology

mediation.

51

52


After data mediation, Discovery iterates, if needed through last steps until result set is finished.

52

53


Selection is invoked to relax result set to finally one service.

53

54


Choreography instance for goal requester is checked for next steps.

54

55


Result is returned to Com. Man. to be forwarded to the service requester.

55

56


Set of Web Service descriptions expressed in WSML sent to adapter.

56

57


Set of Web Service descriptions expressed in requester’s own format returned to goal requester.

57

58

SUMMARY

58

59

Summary

•  The Semantic Web provides a mechanism for –  Representing knowledge on the Web –  Annotating data on the Web –  Annotating services on the Web

•  Everything is identified by a URI •  RDF to assert relations between resources •  RDFS and OWL to make statements about types •  SPARQL to query RDF data •  WSMO as a conceptual model •  WSML for describing services at different levels of expressivity •  WSMX as a Semantic Execution Environment for bringing requesters

and providers together

59

60

REFERENCES

60

61

References

•  Semantic Web Primer: http://www.ics.forth.gr/isl/swprimer/ •  Linked Open Data: http://linkeddata.org/ •  Linked Open Data Tutorial:

http://www4.wiwiss.fu-berlin.de/bizer/pub/LinkedDataTutorial/ •  WSMO: http://www.wsmo.org/TR/d2/ •  WSML: http://www.wsmo.org/TR/d16/d16.1/ •  WSMO/WSML Tutorials: http://wiki.sti2.at/index.php?title=WSMT_Tutorials

•  Wikipedia: –  URI: http://en.wikipedia.org/wiki/URI –  RDF; http://en.wikipedia.org/wiki/Resource_Description_Framework –  RDFS: http://en.wikipedia.org/wiki/RDFS –  SPARQL: http://en.wikipedia.org/wiki/SPARQL –  WSMO: http://en.wikipedia.org/wiki/WSMO –  WSML: http://en.wikipedia.org/wiki/Web_Services_Modeling_Language

61

62 62

Exam Preparation

•  Exam will take place on the 1st of February 2010, 14:15 in room HG. •  Exam time is 90 minutes •  The material for exam are the slide sets:

Title Introduction

Propositional Logic

Predicate Logic

Theorem Proving, Description Logics and Logic Programming

Search Methods

CommonKADS

Problem Solving Methods

Planning

Agents

Rule Learning

Inductive Logic Programming

Semantic Web and Exam Preparation

63 63

Questions?

Documents

Semantic Web and Exam Preparation - STI Innsbruck...• Semantic Web Services are a layer on top of existing Web service technologies and do not aim to replace them • Provide a formal