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RDF

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RDF & SPARQL Introduction Dongfang Xu Ph .D student, School of Information, University of Arizona Sept 10, 2015 – PowerPoint PPT presentation

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Title: RDF


1
RDF SPARQLIntroduction
  • Dongfang Xu
  • Ph .D student, School of Information, University
    of Arizona
  • Sept 10, 2015

2
Catalog
Semantic Web
1
RDF
2
RDF Schema
3
SPARQL
4
3
Semantic Web
  • The Limits of todays Web (2.0)
  • 1.High recall and low precision
  • 2. Low recall and even on recall
  • 3. Results are highly sensitive to vocabulary.
  • 4. Single Web pages.
  • Reference Antoniou, G., Van Harmelen, F.
    (2008). A semantic web primer (2nd ed.).
    Cambridge, Mass MIT press.

4
Semantic Web
An Example
What can be done?
5
Semantic Web
  • The Semantic Web Technologies
  • (standard technologies )
  • Format the web content.
  • Relate the data
  • Machine-processable web information

6
Semantic Web
An Example
ltcompanygt lttreatmentOfferedgtPhysiotherapylt
/treatment Offeredgt ltcompanyNamegtAgilitas
Physiotherapy Centrelt/companyNamegt
ltstaffgt lttherapistgtLisa
Davenportlt/therapistgt
lttherapistgtSteve Matthewslt/therapistgt
ltsecretarygtKelly Townsendlt/secretarygt
ltstaffgt lt/companygt
7
XML RDF
ltcourse nameDiscrete Mathematicsgt
ltlecturergtDavid Billinglt/lecturergt lt/coursegt ltlec
turer namelecturergtDavid Billinggt
ltteachesgt Discrete Mathematicslt/teachesgt lt/lecture
rgt ltteachingOfferinggt ltlecturergtDavid
Billinglt/lecturergt ltcoursesgt Discrete
Mathematicslt/coursesgt lt/teachingOfferinggt
XML does not provide any means of talking about
the semantics (meaning) of data
8
Catalog
Semantic Web
1
RDF
2
RDF Schema
3
SPARQL
4
9
RDF
  • What is RDF?
  • A data model for objects (resources) and
    relations between them
  • Provides a simple semantics for the data model
  • The model can be represented in an xml syntax.
  • Basic building block is an object-attribute-value
    triple, called statement.

An Example
10
RDF
11
RDF Data Model
  • As you read the RDF literature you may see the
    following terminology
  • Subject this term refers to the item that is
    playing the role of the resource.
  • predicate this term refers to the item that is
    playing the role of the property.
  • Object this term refers to the item that is
    playing the role of the value.

ltrdfDescription rdfID"Yangtze"
ltunilengthgt6300 kilometerslt/unilengthgt lt/rdf
Descriptiongt
12
RDF resource
  • A Resource is any object identifiable by a URI.
  • 1.Resources can use any URI, e.g.
  • http//www.example.org/file.xmlelement(home)
  • http//www.example.org/file.htmlhome
  • http//www.example.org/file2.xmlxpath1(//q_at_ab)
  • 2. URI-s can also use different forms
  • CIT11111 (http//www.example.org/file.xml
    CIT11111)
  • 3525346
  • 3. The resource is defined like below, with ltrdf
    Descriptiongt
  • Usually
  • ltrdf Description rdf about gtmeans
    referencing an existing resource
  • ltrdf Description rdf ID gtmeans creating a
    new resource

13
RDF resource
An Example
ltrdfDescription rdfaboutCIT1111gt
ltunicourseNamegtDiscrete Mathematicslt/unicour
seNamegt ltuniisTaughtBy
rdfresourse949318/gt lt/ rdfDescription
gt ltrdfDescription rdfID949318gt
ltuninamegtDavid Billlt/uninamegt
ltunititlegt Associate Professorlt/unititlegt lt/
rdfDescription gt Resource reference
14
RDF property value
Property value must be a Literal or a Resource
An Example
ltunicourseNamegtDiscrete Mathematicslt/unicourseNa
megt
property
Value
ltrdftype rdfresource unilecturer/gt

15
RDF element
  • Root element ltrdf RDF namespacegt
  • ltrdfRDF
  • xmlnsrdf"http//www.w3.org/1999/02/22-rdf
    -syntax-ns" xmlnscd"http//www.recshop.fake/cd
    "gt
  • 2. Description element define resource
  • 3. Property eelement define attribute
  • 4. Bag/Seq/Alt element define a few attributes
    within the property.
  • See more http//www.w3schools.com/webservices/ws_
    rdf_main.asp

16
Catalog
Semantic Web
1
RDF
2
RDF Schema
3
SPARQL
4
17
RDF Schema
  • RDF schema is a vocabulary description language
    for describing properties and classes of RDF
    resources, with a semantics for generalization
    hierarchies of such properties and classes.
  • RDF Schema is a primitive ontology language.
  • RDFS will use RDF itself to define the semantics
    of particular domain.

18
RDF Schema
19
Catalog
Semantic Web
1
RDF
2
RDF Schema
3
SPARQL
4
20
SPARQL
  • SPARQL is the query language to search resource
    value
  • It is based on matching graph patterns ( like RDF
    triple pattern, but the resource and value can be
    variable)
  • ?res uniphone ?pho
  • use ? to define variable, for both string and
    numeric type
  • Like in SQL, it has a Select-From-Where
    structure.

21
SPARQL
An Example
PREFIX rdf lt http//www.w3.org/1999/02/22-rdf-syn
tax-ns gt PREFIX unilthttp//www.mydomain.org/uni-
nsgt (namespace make quries shorter and easier to
read) Select ?X Where ?x uni phone
520-543-2340.
22
SPARQL
An Example
Select ?X ?Y Where ?x uni phone ?y
23
SPARQL
An Example
Select ?name ?Y Where ?X rdftype
uniLecturer uni name ?name.
?X uni phone ?Y.
24
SPARQL
An Example
Select ?name ?Y Where ?X rdftype
uniLecturer uni name ?name.
?X uni phone ?Y. OPTIONAL?X
uniphone ?Y
25
SPARQL
An Example
Select ?Y Where ?X rdftype
uniLecturer uni name David
Bill. ?C uni phone ?Y.
Filter(?X?C)
26
SPARQL
27
SPARQL
28
SPARQL
29
SPARQL
30
SPARQL
  • SPARQL has several query forms.
  • The CONSTRUCT query form returns an RDF graph.

31
SPARQL
More resources http//www.w3.org/TR/rdf-sparql-q
uery/docResultDesc http//rdf.myexperiment.org/ho
wtosparql https//jena.apache.org/tutorials/sparql
.html
32
Thank you!
QA
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