semanticweb examples

7/30/2019 semanticweb examples

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Thomas Schmidt

schmidt@informatik.

haw-hamburg.de

Semantic Web Technologies:Examples

Representing Knowledge:

Modelling Thesauri and such Web Ontology Language for Services (OWL-S)

The Semantic of Hyperlinks


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deRepresenting Knowledge

In the Semantic Web we want to discover and apply knowledge

More specifically: we want to built ontologies from existing knowledgeand use these for inference

Practical approach:

- Take available taxonomies, thesauri, etc. and

formulate them in OWL

- Use reasoner to apply OWL model

Inject knowledge into applications


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.de

Example:

ACM Computing

Classification System


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deSimple RDFS Approach:

ACM (XML):

Hardware

ControlStructures

ControlDesign Styles

rdfs:subClassOF

rdfs:subClassOF

OWL:


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deACM Relations


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deAdditional Property: Relation

Not expressible in a class hierarchy

Can be characterised in OWL & applied

transitive, symmetric

But: class-valued ( rdf:type ) OWL Full needed

Expression of simple thesauri problematic in OWL


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deA Simpler Example

Books on

Lions:

:TheAfricanLionBooka :Book ;:bookTitle "The African Lion" ;

dc:subject :AfricanLion

:AfricanLiona owl:Class;rdfs:subClassOf :Lion

Typical problem:

:BookAboutAnimalsa owl:Class ;rdfs:subClassOf[ a owl:Restriction ;owl:someValuesFrom :AnimalClass ;owl:onProperty dc:subject

]


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deOWL DL Approaches (I)

Individuals inparallel

:LionsLifeInThePrideBooka :Book ;:bookTitle "Lions: Life in the Pride" ;dc:subject :LionSubject

Now:

:BookAboutAnimalsa owl:Class ;rdfs:subClassOf[ a owl:Restriction ;

owl:someValuesFrom :Animal ;owl:onProperty dc:subject

]


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deOWL DL Approaches (II)

Unspecified

class members

:LionsLifeInThePrideBook

a :BookAboutAnimals ;[ a owl:Restriction ;owl:onProperty dc:subject ;owl:someValuesFrom :Lion

];

:bookTitle "Lions: Life in the Pride" ;

Now:

BookAboutAnimals predefined

http://www.w3.org/TR/swbp-classes-as-values/


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Use case:

ACM Computing Classification System

Thomas Schmidt

schmidt@informatik.

haw-hamburg.de

ACMCCS 1998 (latest version)http://www.acm.org/class

Widely used in classification ofconference papers and articles incomputer sciences.

Structure:

11 first level nodes

Each list of children for a first orsecond level node contains atleast one General (0) node and

one Miscellaneous (m) node.

Contains see also referencesbetween certain nodes

Represent in processableOntology (not OWL Full)

A.

General Literature

A.0

General

A.2

Reference

A.1

Introductory and Survey

A.m

Miscellaneous

A.0.0

Biographies/

autobiographies

A.0.1Conference Proceedings

A.0.2

General literary works


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deUse case: Scenario

Idea

Classify content according to ACMCCS98 Enhance search mechanisms by using ACMCCS98 scheme to

discover related information

ToDo

Add classifier to content

Build ontology representation of ACMCCS98

Implement application logic


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deSKOS

SKOS = Simple Knowledge Organisation Systems

(http://www.w3.org/2004/02/skos/)

Outcome of the European SWAD project

Meta Model for representing thesauri a.s.

Built as RDF Schema with OWL property characteristics

Semantic of Concepts less restrictive than OWL classes

Provides association of (several) words or phrases to concepts
http://www.w3.org/2004/02/skos/http://www.w3.org/2004/02/skos/


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deSKOS

OWL complaint framework for

building concept schemes

Basic constructs:

skos:ConceptScheme

skos:Concept

skos:narrower

skos:broader

skos:related

Knowledge Entities are Concepts,grouped in a Concept Scheme

http://www.w3.org/2001/sw/Europe/reports/thes/1.0/guide/


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deExpressing ACMCCS98 in SKOS


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deA part of the RDF data model


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deCode Fragments:

Obtaining an Inference Model1. Load SKOS schema (from the web):

Model schema = ModelLoader.loadModel(

"http://www.w3.org/2004/02/skos/core.rdf");

2. Load data (ACM instances of SKOS from local file):Model data = ModelLoader.loadModel("acmskos.rdf);

3. Obtain reasoner (SKOS is build upon OWL, so we need an OWL-capable reasoner):Reasoner reasoner = ReasonerRegistry.getOWLReasoner();

4. Binding schema:reasoner = reasoner.bindSchema(schema);

5. Creating Inference Model:InfModel infModel = ModelFactory.createInfModel(reasoner,

data);


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deGetting the non-obvious

//get subject we want information on

Resource subject = infModel.getResource(

http://www.acm.org/class/1998/B.8);

//get type of information (only related concepts)

Property predicate = infModel.getProperty(

"http://www.w3.org/2004/02/skos/core#related");

//get iterator to all statements matching the given conditions

StmtIterator it = infModel.listStatements(subject, predicate,

null);

//get perfLabel of the first statement returned

String label = it.nextStatement().getProperty(

http://www.w3.org/2004/02/skos/core#prefLabel).getString()


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deUse Case:

eLearning Objects content augmentationIdea

LOM relations expressing connection between eLOs Relations are qualified

Use LOM relations to suggest further content to the learner

ToDo

Map LOM relations into an ontology Implement application logic


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deSimple scheme

representing LOM Relations Relations referencing other eLearning Objects owl:ObjectProperties

All relation qualifiers have an inverse equivalent (eg.isBasisFor isBasedOn) owl:inverseOf

Qualifiers could be declared as being transitive owl:TransitivProperty

S


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deSample Instances

Dexter

Dexter Storage

Amsterdam Hypermedia Model

Th S h idt


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deComfortable Vocabularies

Use the Jena tool schemagen to build vocabulary (java) classes from OWL files(http://jena.sourceforge.net/how-to/schemagen.html)

LOM.Relations.kind is basis for

/**

The ontology model that holds the vocabulary terms
*/
private static OntModel m_model =ModelFactory.createOntologyModel(ProfileRegistry.OWL_LANG );

/**

LOM.Relations.kind is basis for
*/
public static final ObjectProperty isBasisFor =m_model.createObjectProperty("http://hylos.fhtw-berlin.de/HylosLOM#isBasisFor" );

Th S h idt


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deGetting something out of the Inference Model

1. Create Inference Model:Model schema = ModelFactory.loadModel(hylosLOM.owl);

Model data = ModelFactory.loadModel(lomData.rdf);Reasoner reasoner = ReasonerRegistry.createOWLReasoner();

reasoner = reasoner.bindSchema(schema);

InfModel infModel = ModelFactory.createInfModel(reasoner,

data);

2. Querying the model:Resource s = infModel.getResource(AmsteHyperModel.xml);

for( StmtIterator it = infModel.listStatements(s,

HylosLOMVocab.isBasedOn, null); it.hasNext(); ){

System.out.println(PrintUtil.print(it.nextStatement());

}

Thomas Schmidt


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deRules Basis for inference

OWL reasoner is based upon specific rules which model the

OWL assertions and constraints

Applied ruleset could be obtained from FBRuleReasoner viagetRules() : List

Rules are created using Rules.parseRule(String) : Rule

orRules.parseRules(String) : List

For detailed information on the inference system refer to

http://jena.sourceforge.net/inference/index.html

Thomas Schmidt


24/41

Thomas Schmidt

schmidt@informatik.

haw-hamburg.deRule DefinitionRule:= bare-rule.

or [ bare-rule]or [ ruleName : bare-rule]

bare-rule:= term, ... term-> hterm, ... hterm// forward ruleorterm, ... term


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deCreating own rules

If A is based on B and B has part C then A is also based on C[myrule1: (?Ahttp://hylos.fhtw-berlin.de/HylosLOM#isBasedOn

?B) (?B http://hylos.fhtw-berlin.de/HylosLOM#hasPart ?C) ->(?Ahttp://hylos.fhtw-berlin.de/HylosLOM#isBasedOn ?C)]

If A is based on B and B is part of C then A is also based on C[myrule2: (?Ahttp://hylos.fhtw-berlin.de/HylosLOM#isBasedOn?B) (?C http://hylos.fhtw-berlin.de/HylosLOM#isPartOf ?B) ->

(?Ahttp://hylos.fhtw-berlin.de/HylosLOM#isBasedOn ?C)]

Thomas Schmidt


26/41

Thomas Schmidt

schmidt@informatik.

haw-hamburg.deExtending the standard ruleset

String RULE_FILE = own.rules;

//load rules from file own.rulesList rules =

Rule.parseRules(Util.loadResourceFile(RULE_FILE));

//add rules to the existing ruleset

((OWLFBRuleReasoner) reasoner).getRules().addAll(rules);

/*

* bind schema to reasoner

*/

Attention: ruleset has to be loaded before the schema is bound

to the reasoner.

Thomas Schmidt


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deOWL-S

Web Ontology Language for Services

Idea: Provide a computer-interpretable description of a Web Serviceand any means to access it

Ontology Standard consisting of basic classes and properties for

declaring and describing services

Originally DAML-S from DAML Initiative

Release 1.0 by DAML (Nov 2003)

Now: Release 1.1 Submission to W3C

Thomas Schmidt


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Thomas Schmidt

schmidt@informatik.

haw-hamburg.deMotivation + Use Cases

Goals: Enable agents to discover, invoke, verify, interoperate, compose

and monitorWeb Services:

1. Automatic Web Service Discovery: Enable declarative advertisements

of properties and capabilities

Find a service, that sells skiing lift tickets for my place and accepts credit cards

2. Automatic Web Service Invocation: Provide standard means for

specifying declarative APIs and parameter semantics

Buy me that lift ticket using my credit card

3. Automatic Webs Service Composition and Interoperation: Provide

declarative specifications of prerequisites & consequences of apps.

and a language to describe composition and data flow interactionDetermine the place with best snow height and then buy me the lift card

Thomas Schmidt


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schmidt@informatik.

haw-hamburg.deOntology Structuring for Services

Three essential types of knowledge about a service:

What does the service provide?Profile class used to advertise services

How is it used?

ServiceModel class usedto describe the process model

How to interact with it?ServiceGrounding class specifies

details of accessing the service

Thomas Schmidt


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schmidt@informatik.

haw-hamburg.deService Profile

A description of services as offered by providers or needed by

requestors

The profile provides a detailed description of a service to a registry,

but is useless after service selection ( ServiceModel)

Three types of information:

- Provider information: Service Name, Contact, Description

- Functional description: Input, Output, Precondition, Effects

- Additional properties: Attributes, Parameters, Categories

Thomas Schmidt


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schmidt@informatik.

haw-hamburg.deService Profiles

Thomas Schmidt


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schmidt@informatik.

haw-hamburg.deService Model

Models Services as Processes

Two types of processes: Atomic or Composite

Describes:

- Parameters (Input, Output) & Expressions (Precondition, Effects)- Process Type

- Process composition

- Data flow and parameter binding

Thomas Schmidt


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schmidt@informatik.

haw-hamburg.de

Thomas Schmidt


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schmidt@informatik.

haw-hamburg.deService Grounding

Concrete service access description

Extends WSDL on atomic processes

Extensions:

- WSDL message may use owl-sparameter objects

- EncodingStyle may be OWL

- Process composition

- OWL-S process attribute may

be used as WSDL operation element

Thomas Schmidt

h idt@i f tik


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schmidt@informatik.

haw-hamburg.deThe Semantic of a Hyperlink

Links encode relations between resources

Problem: What is their semantic interpretation?

Get information from

- Departure & arrival of a link

- Contextual information of the link itself

Treat links as separate semantic statements to

- Process Links in applications

- Retrieve information about resources

Thomas Schmidt

h idt@i f tik


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schmidt@informatik.

haw-hamburg.deLinking & Anchoring

Ingredients of a link


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schmidt@informatik.

haw-hamburg.deInteractivity + Relation

Hyper references are constructed from:

Anchors marking data chunks in documents

Links connecting anchors

Anchors and Links need not to be stored inside the documents

XLink (2001)

W3C Standard for creating and describing links

Bidirectional and multidirectional links Semantic attributes (title, arcrole, )

Thomas Schmidt

schmidt@informatik


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schmidt@informatik.

haw-hamburg.deDeriving statements from Meta Data

This page is titled

hamster diseases

Subject Predicat

Object

Anchors provideadditional specification

Thomas Schmidt

schmidt@informatik


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schmidt@informatik.

haw-hamburg.deBuilding Link Semantic

Anchored content carries (RDF-) semantics

This part is about hamsters having hay fever

Simple link statement

This part titled Hay Fever handbookrepresents

background information onthis part about hamstershaving hay fever

Higher order statementLink1 says thatthe part titled Hay Fever Handbookrepresents background information onthe partabout hamsters having hay fever.

Thomas Schmidt

schmidt@informatik


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schmidt@informatik.

haw-hamburg.deDeriving statements from Meta Data

Thomas Schmidt

schmidt@informatik

f


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schmidt@informatik.

haw-hamburg.deReferences

Semantic Web @ W3C - http://www.w3.org/2001/sw/

OWL Semantics & Abstract Syntax - http://www.w3.org/TR/owl-semantics/

Representing Classes As Property Values on the Semantic Web -http://www.w3.org/TR/swbp-classes-as-values

SKOS-Core 1.0 Guide -

http://www.w3.org/2001/sw/Europe/reports/thes/1.0/guide Jena Javadoc - http://jena.sourceforge.net/javadoc/

D. Martin et. al.: OWL-S: Semantic Markup for Web Services, W3C Submission

http://www.w3.org/Submission/2004/SUBM-OWL-S-20041122/

DAML Services - http://www.daml.org/services/owl-s/

P. Alesso, C. Smith: Developing Semantic Web Services, Peters, 2005
http://www.w3.org/2001/sw/http://www.w3.org/TR/owl-semantics/http://www.w3.org/TR/swbp-classes-as-valueshttp://www.w3.org/2001/sw/Europe/reports/thes/1.0/guidehttp://www.w3.org/2001/sw/Europe/reports/thes/1.0/guidehttp://jena.sourceforge.net/javadoc/http://www.w3.org/Submission/2004/SUBM-OWL-S-20041122/http://www.daml.org/services/owl-s/http://www.daml.org/services/owl-s/http://www.daml.org/services/owl-s/http://www.w3.org/Submission/2004/SUBM-OWL-S-20041122/http://jena.sourceforge.net/javadoc/http://www.w3.org/2001/sw/Europe/reports/thes/1.0/guidehttp://www.w3.org/TR/swbp-classes-as-valueshttp://www.w3.org/TR/owl-semantics/http://www.w3.org/2001/sw/

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