Programming with - PowerPoint Presentation

Slide1

Programming with Jena

Sources for examples can be found @http://jenabean.googlecode.com/svn/jenabean-lab1http://jenabean.googlecode.com/svn/jenaclass

Taylor CowanTravelocity8982Slide2

2

[] a foaf:Person;foaf:name Taylor Cowan;foaf:weblog <http://thewebsemantic.com>;foaf:workplaceHomepage

<http://www.travelocity.com>;foaf:holdsAccount <http://twitter.com/tcowan>;foaf:currentProject <http://jenabean.googlecode.com>;foaf:currentProject <http://geosparql.googlecode.com>;foaf:currentProject <http://jo4neo.googlecode.com>;Slide3

3

Model m = ModelFactory.createDefaultModel();Thing

todaysTopic = new Thing("http://jenabean.googlecode.com", m);new Thing(m).isa(

Foaf.Person.class)

.name(

"Taylor Cowan"

)

.weblog(

URI.

create("http://thewebsemantic.com")) .holdsAccount(URI.create("http://twitter.com/tcowan")) .currentProject(todaysTopic) .currentProject(URI.create("http://jo4neo.googlecode.com"));

@see

Card.java in package

example.fluentwriterSlide4

4

AGENDASemantic Web IntroductionRDF basicsCoding Towards Jena’s Semantic Web Framework APIJava to Model Binding with JenaBean

Java to Model Binding with Fluent InterfacesSlide5

Why Not Microformats?

5<

xsl:choose><xsl:when test="(false() = not((.//*[not(ancestor-or-self::*[local-name() = 'del']) = true() and contains(concat(' ',normalize-space(@class),' '),' fn ') and (local-name() = 'img' or local-name() = 'area')]/@alt) and (string-length(normalize-space(.//*[not(ancestor-or-self::*[local-name() = 'del']) = true() and contains(concat

(' ',normalize-space(@class),' '),' fn ') and (local-name() = 'img' or local-name() = 'area')]/@alt)) = string-length(translate(normalize-space(.//*[not(ancestor-or-self::*[local-name() = 'del']) = true() and contains(

concat

(' ',normalize-space(@class),' '),' fn ') and (local-name() = '

img

' or local-name() = 'area')]/@alt),' ',''))))) or (false() = not((.//*[not(ancestor-or-self::*[local-name() = 'del']) = true() and contains(

concat

(' ',normalize-space(@class),' '),' fn ') and (local-name() = 'abbr')]/@title) and (string-length(normalize-space(.//*[not(ancestor-or-self::*[local-name() = 'del']) = true() and contains(concat(' ',normalize-space(@class),' '),' fn ') and (local-name() = 'abbr')]/@title)) = string-length(translate(normalize-space(.//*[not(ancestor-or-self::*[local-name() = 'del']) = true() and contains(concat(' ',normalize-space(@class),' '),' fn ') and (local-name() = 'abbr')]/@title),' ',''))))) or (false() = not((.//*[not(ancestor-or-self::*[local-name() = 'del']) = true() and contains(concat(' ',normalize-space(@class),' '),' fn ') and not(local-name() = 'abbr' or local-name() = 'img')]) and (string-length(normalize-space(.//*[not(ancestor-or-self::*[local-name() = 'del']) = true() and contains(concat(' ',normalize-space(@class),' '),' fn ') and not(local-name() = 'abbr' or local-name() = 'img' or local-name() = 'area')][1])) = string-length(translate(normalize-space(.//*[not(ancestor-or-self::*[local-name() = 'del']) = true() and contains(concat(' ',normalize-space(@class),' '),' fn ') and not(local-name() = '

abbr

' or local-name() = '

img

')][1]),' ','')))))

">

http://suda.co.uk/projects/microformats/hcard/xhtml2vcard.xslSlide6

RDF != XML

“The site at http://www.travelocity.com, also known as Travelocity, is an online travel agency competing with expedia.com”6Slide7

Concepts as a Directed Graph

7Slide8

8

Concepts Serialized as N3:OnlineTravelAgency a owl:Class

.:hasCompetitor a rdf:Property .<http://www.travelocity.com> a :OnlineTravelAgency ; rdfs:label

"Travelocity"@en ; :hasCompetitor

<http://www.expedia.com> .Slide9

9

Concepts Serialized as RDF/XML<rdf:RDF …

>  <owl:Class rdf:about="http://foo#OnlineTravelAgency"/> 

<rdf:Property

rdf:about

=

"http://foo#hasCompetitor"

/>

<OnlineTravelAgency rdf:about="http://www.travelocity.com">    <hasCompetitor rdf:resource="http://www.expedia.com"/>    <rdfs:label xml:lang="en"

>

Travelocity

</

rdfs:label

>

</

OnlineTravelAgency

>

</

rdf:RDF

>Slide10

As N-Triples (Most Canonical or Normalized)

<hasCompetitor> <

rdf:type> <rdf:Property> .<http://travelocity.com> <hasCompetitor

> <http://expedia.com>.

<http://travelocity.com>

<

rdfslabel

>

"Travelocity"@en

<http://travelocity.com> <rdf:type> <OnlineTravelAgency> .<OnlineTravelAgency> <rdf:type> <owl:Class> .10

Subject

,

Verb

, Object = a tripleSlide11

As Java Code, using the Jena API

OntModel m = ModelFactory.createOntologyModel();

OntClass ota = m.createClass("OnlineTravelAgency");Individual

tvly =

ota.createIndividual

(

"http://www.travelocity.com"

);

tvly.setLabel

("Travelocity", "en");OntProperty p = m.createOntProperty("hasCompetitor");tvly.setPropertyValue(p, m.createResource("http://www.expedia.com"));11Slide12

Creating a Model

1: Model m = ModelFactory.createDefaultModel();

2: m.setNsPrefix("foaf", FOAF.NS);3: Resource jazoon

= m.createResource

(

"http://jazoon.com/"

);

4: Resource java =

m.createResource

(5: "http://dbpedia.org/resource/Java_(software_platform)");6: jazoon.addProperty(FOAF.primaryTopic, java);7: m.write(System.out, "N3");12

<http://jazoon.com/>

foaf:primaryTopic

<http://dbpedia.org/resource/Java_(software_platform)> .Slide13

Assertion

13

jazoon.comj

ava

foaf:primaryTopicSlide14

Creating an Inferencing Model

OntModel infModel =

ModelFactory.createOntologyModel( OntModelSpec.OWL_MEM_MICRO_RULE_INF, m);infModel.read("http://xmlns.com/foaf/spec/index.rdf"

);infModel.writeAll

(

System.

out

,

"N3"

,null);14<http://dbpedia.org/resource/Java_(software_platform)> foaf:isPrimaryTopicOf <http://jazoon.com/>In addition to known data, a new triple is inferred…Slide15

Knowledge after Inference

15

jazoon.comj

ava

foaf:primaryTopic

foaf:isPrimaryTopicOf

foaf:Document

Is a Slide16

16

The Semantic Web is Property focusedProperties have Classes, not vice versaDon’t read “the domain of foaf:knows is a foaf:Person”, but instead “anything with foaf:knows

relationship is a foaf:Person”Properties can extend other propertiesProperties can be declared as inverse, symmetric, and transitive, all resulting in new inferences.Slide17

List All Classes from an Ontology

OntModel model = ModelFactory.createOntologyModel();

model.read("http://xmlns.com/foaf/spec/index.rdf");ExtendedIterator<OntClass> it = model.listClasses();

while(

it.hasNext

()) {

OntClass

cls = it.next(); if (cls.getNameSpace().equals(FOAF.NS)) System.out.println(cls.getURI());}17Slide18

Models Can be Populated from URL, Either Public or Local

OntModel model = ModelFactory.createOntologyModel();// read from URLmodel.read

("http://xmlns.com/foaf/spec/index.rdf"); model.read("file:mydata.n3","N3");

18Slide19

Models can be Populated from Other Models

Model modelA = ModelFactory.createDefaultModel

();Model modelB = ModelFactory.createDefaultModel();…//Add all statements from modelB

to modelA

modelA.add

(

modelB

);

19Slide20

20

Some example foaf:<http://www.ibm.com/developerworks/xml/library/j-jena/> a

dc:Article ; dc:creator "Philip McCarthy"^^xsd:string ; dc:subject "jena, rdf, java, semantic web"^^

xsd:string ;

dc:title

"Introduction to Jena"^^

xsd:string

.Slide21

21

Equivalent Raw Jena API Client CodeString NS = "http://purl.org/dc/elements/1.1/";

OntModel m = ModelFactory.createOntologyModel();OntClass articleCls = m.createClass(NS +

"Article");

Individual

i

=

articleCls.createIndividual

(

"http://www.ibm.com/developerworks/xml/library/j-jena/");Property title = m.getProperty(NS + "title");Literal l = m.createTypedLiteral("Introduction to Jena");i.setPropertyValue(title,l);Property creator = m.getProperty(NS + "creator"

);

l =

m.createTypedLiteral

(

"Philip McCarthy"

);

i.setPropertyValue

(

creator,l

);

Property subject =

m.getProperty

(NS +

"subject"

);

l =

m.createTypedLiteral

(

"

jena

,

rdf

, java, semantic web"

);

i.setPropertyValue

(

subject,l

);

m.write

(

System.

out

,

"N3"

);Slide22

22

Pain Points of Raw Jena API ProgrammingYou need to create unique URI’s for every entity.You must specify the type of each primitive value.Properties must be created for each bean property.The impedance mismatch is similar to what we had with RDBMSSlide23

23

Creating The Same Assertions with JenaBeanModel m = ModelFactory.createDefaultModel

();Bean2RDF writer = new Bean2RDF(m);Article article = new Article(

"http://www.ibm.com/developerworks/xml/library/j-jena/"

);

article.setCreator

(

"Philip McCarthy"

);

article.setTitle("Introduction to Jena");article.setSubject("jena, rdf, java, semantic web");writer.save(article);m.write(System.out, "N3");Slide24

24

The JenaBean ProjectHosted at Google codeBean binding, not code generationDoesn’t use byte code interweavingDoesn’t require implementing an interface

http://jenabean.googlecode.comSlide25

25

Programming with JenaBean is SimpleBean2RDF writes objectsRDF2Bean reads objects3 Annotations

@Id specifies unique field@Namespace provides a domain@RdfProperty maps java properties to RDF propertiesSlide26

The Simplest Possible Example

package examples.model;

import thewebsemantic.Id;public class Person { @Id private

String email

;

public

String

getEmail

() { return email;} public void setEmail(String email) { this.email = email;}}26

<http://examples.model/Person>

a <http://www.w3.org/2000/01/rdf-schema#Class> ;

<http://thewebsemantic.com/javaclass> "

examples.model.Person

" .

<http://examples.model/Person/thewebsemantic@gmail.com>

a <http://examples.model/Person> ;

<http://examples.model/email> "thewebsemantic@gmail.com"^^

xsd:string

.Slide27

Saving an Instance of Person

Model m = ModelFactory.createOntologyModel(); Bean2RDF writer = new Bean2RDF(m); Person p = new Person();

p.setEmail("person@example.com"); writer.save(p); m.write(System.out, "N3"); …<http://example/Person> a

owl:Class ;

<http://thewebsemantic.com/javaclass> "

example.Person

" .

<http://example/Person/taylor_cowan@yahoo.com> a <http://example/Person> ;

<http://example/email> "taylor_cowan@yahoo.com"^^

xsd:string .27Slide28

Overriding the Default Namespace

package examples.model;

import thewebsemantic.Id;import thewebsemantic.Namespace;@

Namespace(

"http://mydomain#"

)

public

class

Person { … }28<http://mydomain#Person> a <http://www.w3.org/2000/01/rdf-schema#Class> ; <http://thewebsemantic.com/javaclass> "examples.model.Person" .<http://mydomain#Person/thewebsemantic@gmail.com> a <http://mydomain

#Person> ;

<

http://mydomain

#email>

"thewebsemantic@gmail.com"^^

xsd:string

.Slide29

Overriding the Default Property Bindings

@Namespace(“http://mydomain#”)public class

Person { private String email; @RdfProperty(FOAF.NS +

"name")

private

String

name

;

29<http://mydomain#Person> a <http://www.w3.org/2000/01/rdf-schema#Class> ; <http://thewebsemantic.com/javaclass> "examples.model.Person" .<http://mydomain#Person/thewebsemantic@gmail.com> a <http://mydomain#Person> ; <http://xmlns.com/foaf/0.1/name> "Taylor Cowan"^^xsd:string .Slide30

Extending Person to Support Friendship

public Collection<Person> friends = new

LinkedList<Person>();@RdfProperty("http://xmlns.com/foaf/0.1/knows")public Collection<Person> getFriends

() { return

friends

;}

30Slide31

Loading Beans from a Model

RDF2Bean reader = new RDF2Bean(m);Person p = reader.load

(Person.class,"person@example.com");Collection<Person> allPeople = reader.load

(Person.class

);

31Slide32

JenaBean Support for OWL Entailments

32

public class Location {

@Id

public

String

id

; public String name;

@

RdfProperty

(transitive=

true

)

public

Collection<Location>

within

;

@

RdfProperty

(

inverseOf

=

"within"

)

public

Collection<Location>

contains

;

…

<http://example.transitive/within>

a

rdf:Property

,

owl:TransitiveProperty

.

<http://example.transitive/contains>

a

rdf:Property

;

owl:inverseOf

<http://example.transitive/within> .Slide33

Reading Existing RDF/OWL

33

Up till this point we were generating the triplesJenaBean + annotations controlled the URI’sThe model knew the provenance of all data (the originating java class)Slide34

Example Geonames “feature” entry

34<Feature rdf:about="http://sws.geonames.org/3333156/

"> <name>London Borough of Islington</name> <alternateName xml:lang="fr">Islington</alternateName> <inCountry rdf:resource="http://www.geonames.org/countries/#GB"/> <population>185500</population> <wgs84_pos:lat>51.5333333</wgs84_pos:lat> <wgs84_pos:long>-0.1333333</wgs84_pos:long> </Feature>

Jenabean

will bind to existing URI’sSlide35

Crafting beans for existing RDF requires care

35@Namespace("http://www.geonames.org/ontology#"

)public class Feature { @Id private URI uri; @

RdfProperty("http://www.w3.org/2003/01/geo/wgs84_pos#lat"

)

public

double

lat;12

3

4

Namespace must accurately match

Your java’s

classname

must match the

Ontology class

Your @Id must be of type

java.net.URI

All property

URI’s must match the Ontology propertySlide36

JenaBean can auto discover JenaBeans, provided it knows the package(s)

361: Model m = ModelFactory.

createDefaultModel();2: m.read("http://ws.geonames.org/search?q=london&type=rdf");3: RDF2Bean reader = new RDF2Bean(m);4: reader.bindAll

("com.foo"

,

"com.bar"

);

// type safe binding by class

reader.bind

(Feature.class);// or packagereader.bind(Feature.class.getPackage());Slide37

JenaBean tip: handling lang encoded strings

If your data has something like this: <alternateName xml:lang="es">Londres</alternateName>Then use JenaBean‘s special type “LocalizedString“

37public Collection<LocalizedString> alternateName;

example.geonamesSlide38

Query Support

38// load using a Jena Resourcereader.load(

Human.class, jenaResource);// load any node using it’s URIreader.load(Human.class, "http://any.uri"

);

Most

most

practical purposes there’s no need to utilize anything other than Jena’s ARQ

api

to query.

JenaBean’s reader (RDF2Bean) can transform a node given it’s URI or it’s representation as a jena Resource…Slide39

thewebsemantic.Sparql Util

39String query = "prefix ntn: <http://semanticbible.org/ns/2006/NTNames#>\n"

+"SELECT ?s WHERE { ?s a ntn:Woman }";Model m = ModelFactory.createOntologyModel();m.read("file:NTNames.owl");m.read

("file:NTN-individuals.owl"

);

RDF2Bean reader =

new

RDF2Bean(m);

reader.bindAll

("example.query");Collection<Woman> women = Sparql.exec(m, Woman.class, query);for (Human human : women) System.out.println(human.label +

":"

+

human.

comment

);

example.querySlide40

Summary

@Namespace(“http://yournamespace.goes.here”)Applies to class declaration@IdApplies to field or getter methodShould be a String or primitive type, or wrapper typetype java.net.URI is special

@RdfProperty(“http://specific.property.uri”)Applies to field or getter methodRemember: by definition, JavaBeans must have a default constructor.40Slide41

Summary

writer.save(mybean)writer.saveDeep(mybean) Save this and all related objectsreader.load(Class.class

, key);reader.loadDeep(…); take care, could place entire graph into memory.reader.bindAll(package, package, …); Makes jenabean aware of your beans41Slide42

JenaBean Fluent Programming API

42

AKA method chaining, foo.this().that().bar();A “Fluent Interface” aims to provide more readable codeA significant departure from JavaBeans

Is

always connected to the

jena

graph

Entirely interface (not class) driven

Allows Individuals to morph into their various classes

Allows use of vocabulary terms against any Individual regardless of classification.Slide43

Example: wgs84 geo vocabulary

43import thewebsemantic.As

;import thewebsemantic.Functional;import thewebsemantic.Namespace;@Namespace("http://www.w3.org/2003/01/geo/wgs84_pos#"

)public

interface

Geo

extends

As {

interface Point extends Geo{} @Functional Geo lat(float l); Float lat(); @Functional Geo long_(float l); Float long_();}Slide44

A fluent api + good IDE makes things fun

44Slide45

Create a new anonymous iCal event.

45Ical t = new

Thing(m).isa(Ical.Vevent.class);

Create a new

iCal event

with URI

Ical

t =

new

Thing(“http://uri”, m). isa(Ical.Vevent.class);Slide46

Full Example: Creating an iCal event for the meetup

461: Ical.Vevent t =

new Thing(m).isa(Ical.Vevent.class);2: t.uid("event_11978192@meetup.com").3: dtstart

("20100124T200000Z").

4:

dtend

(

"20100124T220000Z"

).

5: summary("Jena Semantic Web…").6: location("Parisoma - …")7: .as(Geo.class).8: lat(37.77f).9: long_(-122.41f);[] a ical:Vevent ; ical:dtend "20100124T220000Z" ; ical:dtstart "20100124T200000Z" ;

ical:location

"

Parisoma

- " ;

ical:summary

"Jena Semantic Web…" ;

ical:uid

"event_11978192@meetup.com" ;

geo:lat

"37.77"^^

xsd:float

;

geo:long

"-122.41"^^

xsd:float

.Slide47

JenaBean comes with a few common vocabulary interfaces

47

thewebsemantic.vocabulary.Foaf

Geo

Ical

DCTerms

Sioc

Skos

Rdfs

ReviewVocab

You

may want to copy and modify in some cases.Slide48

Fluent API summary:

48

Your interface should extend

thewebsemantic.As

Provides

polymorphic “as(Class)” to other

vocabs

.

Provides easy type declaration with “

isa(Class)”Use the @Namespace annotation to bind to the vocabularyName setters according to vocab, taking either an Object (literal) or anther Thing (relationship to other Individuals)Name getters according to vocab, returning the same vocabulary type and taking no arguments.

If the vocabulary term collides

with reserved term (as with long), append a dash.

Plural properties should return a Collection.Slide49

49

Project IdeasCreate your own foaf document using the fluent interface.Integrate Jena/JenaBean with restlets

restlets.orgUse your favorite framework (struts, stripes, spring mvc) and create a user registration screen.Write JenaBeans that bind to jamendo or other music ontology at http://dbtune.orgWrite a foaf crawler beginning with Berners-Lee that traverses his social graph.

cc

nickjohnson

http://flickr.com/photots/npj/Slide50

50

Open Source Tools For Java DevsJava Triple StoresJena (HP Labs)Sesame OpenRDF (Aduna

)MulgaraJava Binding toolsJenaBean (Jena)Jastor (Jena)Owl2Java (Jena)Elmo (Sesame)Empirecc

nickjohnson http://flickr.com/photots/npj/Slide51

Taylor Cowan

http://thewebsemantic.com http://twitter.com/tcowanTravelocity taylor.cowan@travelocity.com