SPARQL-DL - Theory & Practice

SPARQL-DL
Theory & Practice
Adriel Café
aac3@cin.ufpe.br

Summary
1. OWL Basics
2. SPARQL
3. SPARQL-DL
4. Comparison: SPARQL x SPARQL-DL
5. Reasoner's Support for DL
6. Practice
SPARQL-DL: Theory & Practice | Adriel Café <aac3@cin.ufpe.br>

Important
This document was based on W3C specifications
• http://w3.org/2001/sw/wiki/SPARQL-DL
• http://w3.org/TR/sparql11-query
• http://w3.org/TR/sparql11-overview
• http://w3.org/TR/rdf-sparql-query
• http://w3.org/TR/owl-guide
• http://w3.org/TR/owl-features
• http://w3.org/TR/owl-ref
• http://w3.org/TR/owl2-overview
• http://w3.org/TR/owl2-profiles

OWL Basics
Ontology Web Language
• Is an ontology language for the Semantic Web with formally defined
meaning
• Is a W3C standard since 2004
• Written in XML
• Derived from the DAML+OIL
• Developed as a vocabulary extension of RDF
• Provide classes, properties, individuals, data values and are stored as
Semantic Web documents
• OWL Tools
• OWL Syntax Converter (http://owl.cs.manchester.ac.uk/converter)
• OWL Validator (http://owl.cs.manchester.ac.uk/validator)

OWL 1
• Compatible with RDF
• Profiles
• OWL Full (Not DL)
• OWL DL (DL SHOIN(D))
• OWL Lite (DL SHIF(D))
OWL Versions
OWL 2
• Compatible with OWL 1 and RDF
• Profiles
• OWL 2 EL (DL EL++)
• OWL 2 QL (DL-Lite)
• OWL 2 RL (DLP)
• OWL 2 DL (DL SROIQ(D))
Is used informally to refer to ontologies
interpreted using the Direct Semantics
http://w3.org/TR/owl2-direct-semantics

OWL 2 Structure
http://w3.org/TR/owl2-overview/OWL2-structure2-800.png

SPARQL
SPARQL Protocol and RDF Query Language
• Is a SQL-Like language for querying RDF data
• Is a protocol
• Is a W3C standard since 2008
• Queries consist of triple patterns, conjunctions, disjunctions, and optional
patterns
"SPARQL will make a huge difference“
(Berners-Lee, 2006)

SPARQL in Semantic Web Stack
http://upload.wikimedia.org/wikipedia/en/3/37/Semantic-web-stack.png

SPARQL Query Types
• SELECT
Returns all, or a subset of, the variables bound in a query pattern match.
• ASK
Returns a boolean indicating whether a query pattern matches or not.
• CONSTRUCT
Returns an RDF graph constructed by substituting variables in a set of triple templates.
• DESCRIBE
Returns an RDF graph that describes the resources found.

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT DISTINCT ?name
FROM <http://xmlns.com/foaf/spec/index.rdf>
WHERE {
?x foaf:name ?name
}
ORDER BY ?name
LIMIT 5
OFFSET 10
Anatomy of a SPARQL Query
Triple patterns to be localized
Subject, Predicate and Object
Prefix label associated with an
IRI
Returns all possible bindings of
the provided variables
DISTINCT keyword removes
all redundant bindings
Data sources that should be
consulted
Solution sequences and
modifiers

RDF Definitions
• RDF Triple
Contains three components: subject, predicate and object
<http://com.ex/people#adrielcafe> <http://com.ex/contact#name> “Adriel Café"
• RDF Graph
Is a set of RDF triples
• Triple Pattern
Is like an RDF triple, but with the option of a variable in place of RDF terms (i.e.,
IRIs, literals or blank nodes) in the subject, predicate or object positions
?people <http://com.ex/contact#name> ?name
• Basic Graph Pattern (BGP)
Is a conjunction of a ﬁnite set of triple patterns

SPARQL Subgraph Matching
• The SPARQL query processor will search for sets of triples that match
these triple patterns, binding the variables in the query to the
corresponding parts of each triple.
• Subgraph matching (a.k.a. simple entailment) considers only the graph
structure of RDF for computing query results
• Entailment Regimes
RDFS Entailment Regime, D-Entailment Regime, OWL 2 RDF-Based Semantics, OWL
2 Direct Semantics
“The main mechanism for computing query results in SPARQL is subgraph matching:
RDF triples in both the queried RDF data and the query pattern are interpreted as
nodes and edges of directed graphs, and the resulting query graph is matched to the
data graph using variables as wild cards.”
(Glimm; Krötzsch, 2010)

SPARQL-DL
SPARQL Protocol and RDF Query Language – Description Logics
• Is a distinct subset of SPARQL
• Uses SPARQL syntax
• Is tailored to ontology specific questions
• Is not yet a W3C standard
• Quite expressive language which allows to mix TBox, RBox, and ABox
queries
• Fully aligned with the OWL 2 standard
• Settled on top of the OWL API
http://www.derivo.de/uploads/pics/SPARQL-DL_01.png

SPARQL-DL Abstract Syntax
• A SPARQL-DL query Q is a finite set of SPARQL-DL query atoms and the
query is interpreted as the conjunction of the elements in the set.
Query Type of the query An example query
Q1 Standard TBox query SubClassOf(?c, ex:Student)
Q2 Standard ABox query
Type(?x, and(ex:Student, ex:Employee)),
PropertyValue(?x, ex:name, ?y)
Q3
ABox query with non-
distinguished variables
PropertyValue(?x, ex:hasPublication, _:y),
PropertyValue(:y, ex:publishedAt, _:z),
Type(_:z, not(ex:Workshop))
Q4 Mixed ABox/TBox query
Type(?x, ex:Student),
Type(?x, ?c),
SubClassOf(?c, ex:Employee),
Q5 Mixed ABox/RBox query
ObjectProperty(?p),
PropertyValue(ex:John, ?p, ?v)
(Parsia & Sirin, 2007)

SPARQL-DL Supported Query Patterns
Class(a)
Property(a)
Individual(a)
Type(a, b)
PropertyValue(a, b, c)
EquivalentClass(a, b)
SubClassOf(a, b)
EquivalentProperty(a, b)
SubPropertyOf(a, b)
InverseOf(a, b)
ObjectProperty(a)
DataProperty(a)
Functional(a)
InverseFunctional(a)
Transitive(a)
Symmetric(a)
Reflexive(a)
Irreflexive(a)
SameAs(a, b)
DisjointWith(a, b)
DifferentFrom(a, b)
ComplementOf(a, b)
Annotation(a, b, c)
StrictSubClassOf(a, b)
DirectSubClassOf(a, b)
DirectType(a, b)
StrictSubPropertyOf(a, b)
DirectSubPropertyOf(a, b)

SPARQL-DL Syntax
• Query Types: ASK and SELECT
• Supports union-like statements called "OR WHERE“
• Primitives
• Variable: ?[a-zA-Z]+ (for example ?a, ?myVar)
• Full IRI: <http://example.com>
• Prefixed IRI: [the prefix]:[the suffix]
• Literal: "this is a literal" (escape the character " inside a literal with ")

SPARQL-DL Query Examples
SELECT ?c WHERE { Class(?c) }
SELECT ?x WHERE {
Transitive(?p),
PropertyValue(<http://example.com#myClass>, ?p, ?x)
}
PREFIX wine: http://w3.org/TR/2003/PR-owl-guide-20031209/wine#
SELECT ?i WHERE {
Type(?i, wine:PinotBlanc)
} OR WHERE {
Type(?i, wine:DryRedWine)
}

Query Comparison: SPARQL x SPARQL-DL
• SPARQL
SELECT ?wine ?region WHERE {
?wine wine:locatedIn ?region
}
• SPARQL-DL
PropertyValue(?wine, wine:locatedIn, ?region)
}

• SPARQL
SELECT ?wine ?flavor WHERE {
?wine wine:locatedIn wine:NewZealandRegion .
?wine wine:hasFlavor ?flavor
}
• SPARQL-DL
PropertyValue(?wine, wine:locatedIn, wine:NewZealandRegion),
PropertyValue(?wine, wine:hasFlavor, ?flavor)
}

• SPARQL
SELECT ?wine WHERE {
{
?wine wine:locatedIn wine:NapaRegion
}
UNION
{
?wine wine:locatedIn wine:NewZealandRegion
}
}
• SPARQL-DL
PropertyValue(?wine, wine:locatedIn, wine:NapaRegion)
} OR WHERE {
PropertyValue(?wine, wine:locatedIn, wine:NewZealandRegion )
}

Reasoner's Support for DL
Pellet RacerPro FaCT++ HermiT
OWL-DL Support Yes Yes Yes Yes
OWL 2 Support Yes Yes Partially Yes
Supported
expressivity
SROIQ(D) SRIQ(D-) SROIQ(D) SHOIQ+
Reasoning
algorithm
Tableau Tableau Tableau Hypertableau
Rule Support
Yes (SWRL - DL Safe
Rules)
Yes (SWRL - not
fully supported) &
own rule format
No
Yes (SWRL - DL Safe
Rules)
Licensing
Free / open-source
& Non-Free/ closed-
source
Non-Free/ closed-
source
Free / open-source Free / open-source
Adapted from http://en.wikipedia.org/wiki/Semantic_reasoner

Practice
• Eclipse IDE (Java Project)
http://eclipse.org
• OWL API
http://derivo.de/en/resources/owl-api.html
• SPARQL-DL API
http://derivo.de/en/resources/sparql-dl-api.html
• HermiT OWL Reasoner
http://hermit-reasoner.com
• Wine Ontology
http://krono.act.uji.es/Links/ontologies/wine.owl

Practice
Queries
• Prefix
PREFIX wine: <http://krono.act.uji.es/Links/ontologies/wine.owl#>
• Query 1
SELECT ?class WHERE {
Class(?class)
}
• Query 2
SELECT ?subClass WHERE {
SubClassOf(?subClass, wine:Wine)
}
• Query 3
PropertyValue(?wine, wine:locatedIn, wine:GermanyRegion)
}

Practice
Queries
• Query 4
}
• Query 5
Type(?wine, wine:Wine),
}
• Query 6
PropertyValue(?wine, wine:locatedIn, wine:NewZealandRegion),
PropertyValue(?wine, wine:hasFlavor, ?flavor)
}

Practice
Queries
• Query 7 (DISTINCT Keyword)
SELECT DISTINCT ?producer ?wine WHERE {
PropertyValue(?producer, wine:producesWine, ?wine)
}
• Query 8 (OR WHERE Statement)
Type(?wine, wine:PinotBlanc)
} OR WHERE {
Type(?wine, wine:DryRedWine)
}

Practice
OWL API + SPARQL-DL API + HermiT Reasoner
// Ontology
IRI ontIRI = IRI.create("http://krono.act.uji.es/Links/ontologies/wine.owl");
OWLOntologyManager ontManager = OWLManager.createOWLOntologyManager();
OWLOntology ont = ontManager.loadOntologyFromOntologyDocument(ontIRI);
// Reasoners
OWLReasoner rStructural = new StructuralReasonerFactory().createReasoner(ont);
OWLReasoner rHermit = new Reasoner.ReasonerFactory().createReasoner(ont);
// Query
QueryEngine queryEngine = QueryEngine.create(ontManager, rHermit);
Query query = Query.create(query1);
String result = queryEngine.execute(query).toString();
System.out.println(result);

References
• HORROCKS, I.; PEREZ-URBINA, H.; MOTIK, BORIS. Efficient Query Answering for OWL 2. 2009.
• HORROCKS, I.; PATEL-SCHNEIDER, P. F.; MCGUINNESS, D. L.; WELTY, C. A. OWL: a Description Logic
Based Ontology Language for the Semantic Web. 2007.
• HORROCKS, I.; KOLLIA, I.; GLIMM, B. SPARQL Query Answering over OWL Ontologies. 2011.
• KREMEN1, P.; SIRIN, E. SPARQL-DL Implementation Experience. 2008.
• PARSIA, B.; SIRIN, E. SPARQL-DL: SPARQL Query for OWL-DL. 2007.
• GLIMM, B.; KRÖTZSCH, M. SPARQL Beyond Subgraph Matching. 2010.
• GRAU, B. C.; HORROCKS, I.; MOTIK, B.; PARSIA, B.; PATEL-SCHNEIDER, P.; SATTLER, U. OWL 2: The
Next Step for OWL. 2008.
• DOMINGUE, J.; FENSEL, D.; HENDLER, J. A. Handbook of Semantic Web Technologies. 2011.
• ALLEMANG, D.; HENDLER J. A. Semantic Web for the Working Ontologist. 2011.
• ANTONIOU, G.; VAN HARMELEN, F. Semantic Web Primer. 2008.
• HEBELER, J.; FISHER, M.; BLACE, R.; PEREZ-LOPEZ, A.; DEAN, M. Semantic Web Programming. 2009.

SPARQL-DL - Theory & Practice

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