From the Semantic Web to the Web of Data: ten years of linking up

from the Semantic Web to the Web of Data
ten years of linking up

Lugano 30-03-2010 Davide Palmisano - Fondazione Bruno Kessler

a short ToC

story of a buzzword

concepts and ideas behind it

Linked Data: four rules, billions of opportunities

the server side of the triple: Java and the Semantic Web

successes, failures and hopes

story of a buzzword

“To a computer, the Web is a
ﬂat, boring world devoid
of meaning.”

“A new form of Web content that
is meaningful to computers will
unleash a revolution of new
possibilities”

“The Semantic Web is not a separate Web but an
extension of the current one, in which
information is given well-deﬁned meaning, ”

story of a buzzword

“Adding semantics to the web involves two things:
allowing documents which have information in
machine-readable forms, and allowing links to
be created with relationship values.”

story of a buzzword

typed objects and relationships

machine-readable content metadata

with shared semantics

The Web as a global giant decentralized database


How to represent the knowledge ?


How to represent the knowledge ?

World’s academic communities dealt for
years with knowledge representation

artiﬁcial intelligence, natural language
processing, model management and many
other research ﬁelds largely contributed

some ancestors traced the way


SHOE[1]

“SHOE is an extension to HTML which
allows authors to annotate their web pages
with machine-readable knowledge”
<USE-ONTOLOGY ID="cs-dept-ontology" VERSION="1.0" PREFIX="cs" URL=
"http://www.cs.umd.edu/projects/plus/SHOE/cs.html">

<CATEGORY NAME="cs.Professor" FOR="http://www.cs.umd.edu/users/hendler/">

<RELATION NAME="cs.member">
    <ARG POS=1 VALUE="http://www.cs.umd.edu/projects/plus/">
    <ARG POS=2 VALUE="http://www.cs.umd.edu/users/hendler/">
</RELATION>

<RELATION NAME="cs.name">
   <ARG POS=2 VALUE="Dr. James Hendler">
</RELATION>

John Sowa’s
Conceptual Graphs [2]

(...) they express meaning in a form that is logically
precise, humanly readable, and computationally
tractable (...)

BOY AGNT WALK

“boy walking”


declining such approaches in a

unpredictable

decentralized

potentially incoherent

environment as the Web is

has been the goal of a standardization effort
mainly lead by the W3C


Resource Description Framework RDF

corner stone of the Semantic Web
technology stack

1999, ﬁrst publication

directed and labeled
graphs as data model


everything is univocally identiﬁable with
a Uniform Resource Identiﬁer

a web page, a person, a book, an intangible thing

http://dpalmisano.myopenid.com

http://dbpedia.org/resource/Lugano

http://dbtune.org/myspace/coldplay


relationships between things could be expressed
with a directed, labeled graph

where

nodes could be resources or XMLSchema-typed values

and relationships are identiﬁed also by URIs



http://sws.geonames.org/3165243/



http://xmlns.com/foaf/0.1/based_near


it’s an RDF triple





http://www.geonames.org/ontology#name

Trento




http://www.geonames.org/
ontology#population
http://www.geonames.org/ontology#name

104946
Trento



http://dpalmisano.myopenid.com http://sws.geonames.org/3165243/

XML serialization

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:foaf="http://xmlns.com/foaf/0.1/">

<rdf:Description rdf:about="http://dpalmisano.myopenid.com/">
<foaf:based_near rdf:resource="http://sws.geonames.org/
3165243/"/>
</rdf:Description>

</rdf:RDF>




Turtle serialization

@preﬁx rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@preﬁx foaf: <http://xmlns.com/foaf/0.1/> .

<http://dpalmisano.myopenid.com/> foaf:based_near <http://
sws.geonames.org/3165243/> .




N3 serialization

<http://dpalmisano.myopenid.com/> <http://xmlns.com/foaf/0.1/
based_near> <http://sws.geonames.org/3165243/> .




JSON serialization

{
"http://dpalmisano.myopenid.com" :
{
"http://xmlns.com/foaf/0.1/based_near": [ { "type" : "uri" ,
"value" : "http://sws.geonames.org/3165243/" } ]
}
}




this triple represents a relationship
between two resources

but how we can represent the meaning of
that relationship?

deﬁning vocabularies and ontologies:
RDFSchema and OWL


an “Hello World” RDFSchema vocabulary

rdf:type
http://helloworld.com/ontology/Person
http://helloworld.com/ontology/father
rdf:type

rdf:type
rdf:type

rdfs:Class rdfs:Property


RDFSchema entailment: inferring new statements

http://helloworld.com/ontology/Person
http://helloworld.com/resource/Michele

rdf:type

http://helloworld.com/resource/Davide


RDFSchema entailment: inferring new statements

http://helloworld.com/ontology/Person rdf:type

http://helloworld.com/resource/Michele

rdf:type

http://helloworld.com/resource/Davide


OWL allows to specify other axioms

property cardinality restrictions
classes disjunction
property transitivity
cardinality constraints

but beware: more expressivity means more
reasoning complexity
interested in these topics? give a try to [3]


describe everything...

and more...


RDFa: Bridging the traditional
Web with the Semantic Web

<div rel="dc:creator">

<span typeof="foaf:Person" about="http://foafbuilder.qdos.com/people/
dpalmisano.myopenid.com/foaf.rdf#me">

<a property="foaf:name" rel="foaf:homepage" href="http://
dpalmisano.myopenid.com/">Davide Palmisano</a>

<a rel="foaf:workplaceHomepage"
href="http://www.fbk.eu">Fondazione Bruno Kessler</a>

</span>
</div>


SPARQL: querying the Semantic Web

based on graph pattern matching
SPARQL Protocol and RDF Query
Language
4 different operators: SELECT, DESCRIBE,
ASK and CONSTRUCT



SELECT ?person
WHERE {
?person a foaf:Person.
?person ex:age ?age.
FILTER(?age > 18)
}



“In which university have
studied the founders of
successful IT companies?”

and order them by
frequency...


SELECT DISTINCT ?almaMater, count(?almaMater) as ?frequency
WHERE {
{ {?company a dbpedia-owl:Company} UNION { ?company a
yago:InternetCompaniesOfTheUnitedStates } UNION {?company a
yago:CompaniesBasedInSiliconValley} UNION {?company a
yago:CompaniesListedOnNASDAQ} }
?company dbpedia-owl:numberOfEmployees ?numberOfEmpl.
FILTER (?numberOfEmpl > 0).
OPTIONAL { ?company dbpedia-owl:keyPerson ?keyPerson }
?keyPerson dbpprop:almaMater ?almaMater.
}
ORDER BY DESC(?frequency)


1.
Use URIs to identify things.

2.
Use HTTP URIs so that these things can be
referred to and looked up ("dereference") by
people and user agents.

3.
Provide useful information (i.e., a structured
description - metadata) about the thing when
its URI is dereferenced.

4.
Include links to other, related URIs in
the exposed data to improve discovery of other
related information on the Web.


DBpedia: Wikipedia as a database

extract such structured info and represent it with RDF


let’s do it also for

Internet Movie Database

BBC /programmes

CiteSeer
GeoNames
Musicbrainz

CIA factbook
and for all imaginable data-
intensive traditional Web sites...


RDF is the model

SPARQL is the query language

RDFa is our Trojan horse

Linked Data is the paradigm

how does it ﬁt with Java?


Semantic Web general purposes open sources libraries

Jena[3] - The Semantic Web Java framework

- a RDF API
- parsing and writing RDF in RDF/XML, N3 and N-Triples
- an OWL API
- In-memory storage and persistence layer
- SPARQL query engine
- Schemagen: Java classes from a RDFSchema vocabulary


Jena: creating a model
// URI declarations
String familyUri = "http://family/";
String relationshipUri = "http://purl.org/vocab/relationship/";

// Create an empty Model
Model model = ModelFactory.createDefaultModel();

// Create a Resource for each family member, identiﬁed by their URI
Resource adam = model.createResource(familyUri+"adam");
Resource beth = model.createResource(familyUri+"beth");

// Create properties for the different types of relationship to represent
Property siblingOf = model.createProperty(relationshipUri,"siblingOf");

// Add properties to adam describing relationships to other family members
adam.addProperty(siblingOf,beth);


Jena: querying the model
// Create a new query passing a String containing the RDQL to execute
Query query = new Query(queryString);

// Set the model to run the query against
query.setSource(model);

// Use the query to create a query engine
QueryEngine qe = new QueryEngine(query);

// Use the query engine to execute the query
QueryResults results = qe.exec();

while (results.hasNext()) {
ResultBinding binding = (ResultBinding)results.next();
RDFNode definition = (RDFNode) binding.get("definition");
System.out.println(definition.toString());
Resource concept = (Resource)binding.get("concept");
List wordforms = concept.listObjectsOfProperty(wordForm);
}


other valuable alternatives

Sesame[4] - a generic open source Java framework for
storage and querying of RDF data
- easy, elegant and well documented

jRDF[5] - an RDF library for Java
- notable for IoC support (Spring 2)


getting RDF data

Any23[6] - Anything to Triples
- a library
- a Web service
- a CLI
- allows to extract RDF from various sources:
- Microformats: Adr, Geo, hCalendar, hCard, hListing,
hResume, hReview, License and XFN
- RDF/XML, Turtle and Notation3
- RDF/XML, N3, Turtle and content-negotiated
serialization supported


Any23: rdf extraction

/*1*/ Any23 runner = new Any23();
/*2*/ runner.setHTTPUserAgent("test-user-agent");
/*3*/ HTTPClient httpClient = runner.getHTTPClient();
/*4*/ DocumentSource source = new HTTPDocumentSource(
httpClient,
"http://www.rentalinrome.com/semanticloft/semanticloft.htm"
);
/*5*/ ByteArrayOutputStream out = new ByteArrayOutputStream();
/*6*/ TripleHandler handler = new NTriplesWriter(out);
/*7*/ runner.extract(source, handler);
/*8*/ String n3 = out.toString("UTF-8");


Any23 deals with such documents that already
contains some RDF metadata

extracting the semantics from free-text and
disambiguate terms with links to some Linked Data
cloud it’s another story

a pletora of different services
- AlchemyAPI[7]
- OpenCalais[8]


The world's largest maker of solar inverters announced Monday that
it will locate its first North American manufacturing plant in Denver.

"We see a huge market coming in the U.S.," said Pierre-Pascal
Urbon, the company's chief financial officer.

The company, based in Kassel, north of Frankfurt, Germany, boasts
growing sales of about $1.2 billion a year.


The world's largest maker of solar inverters announced Monday that
it will locate its first North American manufacturing plant in Denver.

"We see a huge market coming in the U.S.," said Pierre-Pascal
Urbon, the company's chief financial officer.

The company, based in Kassel, north of Frankfurt, Germany, boasts
growing sales of about $1.2 billion a year.

http://dbpedia.org/resource/Frankfurt
http://dbpedia.org/resource/Denver
http://dbpedia.org/resource/Kassel


exposed as HTTP Web services they
provide responses in XML, RDF/XML, RDFa
or JSON

Apache UIMA comes with two annotators
for AlchemyAPI and OpenCalais[9]


indexing RDF data

SIREn[10]: Efficient semi-structured Information
Retrieval for Lucene
- a plugin for Lucene
- extends the Lucene query model
- semi-structured search
- structure aware full-text search
- ranked semi-structured search: most relevant results
returned first
- sub-linear average response time
- flexible semi-structured indexing


storing RDF data
commonly known as “triple-stores”[11]

“let me insert triples and make
SPARQL queries above them”

- OpenLink Virtuoso
- 4Store
- Redland
- Jena or Sesame over a RDBMS


JDBC and Virtuoso

boolean more = stmt.execute("sparql select * from <gr> where { ?x ?y ?z }");
ResultSetMetaData data = stmt.getResultSet().getMetaData();
while(more)
{

rs = stmt.getResultSet();

while(rs.next())

{
...

}

more = stmt.getMoreResults();
}


Empire[12]: JPA for RDF

- Object Triples Mapper
- 4Store, Sesame and Jena support
- small annotation framework for tying Java beans
to RDF
-generate Java interfaces for classes described in an
OWL ontology automatically based on domain, range
constraints, cardinality restrictions
- runtime implementation generation
- IoC with Google Guice


crawl the Web
extract RDF from RDFa and
Microformats with Any23

index the data with SIREn

store the data on HBase

in one word: Sindice.com


Linked Data and RDFa seem to be the right
ways to trigger the “network effect” about
the usage of Semantic Web technologies

data.gov.uk


Twine.com

it has been the ﬁrst mainstream consumer
application of Semantic Web.

raised nearly $24mm of venture capital over 2 rounds
gaining users rapidly - faster than Twitter did in it’s early
years
Twine.com is going to be acquired by Evri.com


Twine.com

“I can truly say they present signiﬁcant challenges
both to developers and to end-users.These
challenges all stem from one underlying problem:
Data storage.” - Nova Spivack CEO


GoodRelations: e-commerce on the Web of Data

huge impact on traditional search engines ranking

enabling cross-site product and offerings retrieval

Google rich snippets


GoodRelations: e-commerce on the Web of Data

GoodRelations and RDFa could heavily impact on
traditional SEO techniques

it may be a really powerful traction for an unleashed
usage of RDFa and semi-structured data on the Web

/me

Technologist @ Fondazione Bruno Kessler
Web of Data research Unit

twitter.com/dpalmisano
davidepalmisano.wordpress.com

wed.fbk.eu

a bunch of references
[1] http://www.cs.umd.edu/projects/plus/SHOE/
[2] http://www.jfsowa.com/cg/
[3] http://jena.sourceforge.net/
[4] http://www.openrdf.org/
[5] http://jrdf.sourceforge.net/
[6] http://developers.any23.org/
[7] http://alchemyapi.com
[8] http://opencalais.com
[9] http://incubator.apache.org/uima/
[10] http://siren.sindice.com/
[11] http://en.wikipedia.org/wiki/Triplestore/
[12] http://clarkparsia.com/weblog/2010/02/03/
empire-0-6/

From the Semantic Web to the Web of Data: ten years of linking up

From the Semantic Web to the Web of Data: ten years of linking up

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From the Semantic Web to the Web of Data: ten years of linking up