RDF and SPARQL
Madalina Croitoru
Representing Knowledge
What type of knowledge
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Novels and short stories are books
A book is a document
Every book has an author
A document has a title
A title is a String
Hugo is the author of Notre Dame de Paris
How to represent this using:
• Conceptual Graphs
• Database Model
• RDF(S)
Generally speaking
Facts: Conjunction of positive atoms
{p(x, y), q(y, z, t), p(z, A), q(z, t, B)}
Generally speaking
Facts: Conjunction of positive atoms
{p(x, y), q(y, z, t), p(z, A), q(z, t, B)}
x
1
p
x
y
y
z
A
z
z
t
t
B
y
A
q
p
2
B
1
3
2
z
t
q
Conceptual Graphs - Databases
BoyId
GirlId
BoyId
Name
GirlId
Name
1
2
1
John
2
Eva
Conceptual Graphs - Databases
BoyId
GirlId
BoyId
Name
GirlId
Name
1
2
1
John
2
Eva
RDF(S)???
Representing Knowledge
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•
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Conceptual Graphs
Database Model
RDF(S)
OWL 2…
…
What good to represent knowledge?
• Querying!
• What type of queries?
– Conjunctive queries
– Ontological queries
Facts
Ontological Conjuctive Query
Conjunctive
Answering
╞
Facts: Conjunction of positive atoms
Query
Ontology
Query: Conjunction of positive atoms
Ontological Conjuctive Query Answering
Facts
Ontology
Φ
╞
Conjunctive
Query
Facts ╞ Conjunctive Query
Simple RDF entailment
Database Conjunctive Query Answering
Deduction in the conjunctive, positive,
existential fragment of FOL
Ontological Conjuctive Query Answering
Facts
╞
Ontology
Type
Hierarchy
Every cat is a vertebrate
If two people are brothers then they are relatives
Conjunctive
Query
Facts + Type Hierarchy
╞
Conjunctive Query
RDF(S) entailment
Conjunctive Positive Fragment of FOL
Simple Conceptual Graphs Entailment
Ontological Conjuctive Query Answering
Facts
╞
Ontology
Rules
For every cat there exists a cat who is its mother
Conjunctive
Query
Facts + Rules
╞
Conjunctive Query
Simple Conceptual Graphs Rules
DATALOG +
Conjunction of positive atoms
• Conceptual Graphs
• Database Model
• RDF(S)
Conjunction of positive atoms
• Conceptual Graphs
• Database Model
• RDF(S)
HOW TO QUERY THIS KNOWLEDGE?!?
Conjunction of positive atoms
• Conceptual Graphs – projection (labelled
graph homomorphism)
• Database Model
• RDF(S)
HOW TO QUERY THIS KNOWLEDGE?
Conjunction of positive atoms
• Conceptual Graphs
• Database Model - SQL
• RDF(S)
HOW TO QUERY THIS KNOWLEDGE
Conjunction of positive atoms
• Conceptual Graphs
• Database Model
• RDF(S) - SPARQL
HOW TO QUERY THIS KNOWLEDGE
Codd’s Relational Model
Codd’s Relational Model
RDF
RDF
The "http://en.wikipedia.org/wiki/Tony_Benn",
published by Wikipedia, has for title 'Tony Benn‘
<http://en.wikipedia.org/wiki/Tony_Benn>
<http://purl.org/dc/elements/1.1/publisher>
"Wikipedia"
<http://en.wikipedia.org/wiki/Tony_Benn>
<http://purl.org/dc/elements/1.1/title>
"Tony Benn" .
RDF
The "http://en.wikipedia.org/wiki/Tony_Benn", published by Wikipedia,
has for title 'Tony Benn‘.
<rdf:RDF
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:dc="http://purl.org/dc/elements/1.1/">
<rdf:Description rdf:about="http://en.wikipedia.org/wiki/Tony_Benn">
<dc:title>Tony Benn</dc:title>
<dc:publisher>Wikipedia</dc:publisher>
</rdf:Description>
</rdf:RDF>
SQL for Databases
• SELECT:
– FROM (tables)
– WHERE (predicate)
– GROUP BY (rows)
– HAVING (predicate on GROUP BY rows)
– ORDER BY (columns)
Select Clause example
SELECT *
FROM Book
WHERE price > 100.00
ORDER BY title;
SPARQL
SELECT ?name ?email
WHERE {
?person rdf:type foaf:Person.
?person foaf:name ?name.
?person foaf:mbox ?email.
}
SPARQL
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT
?name ?email
WHERE {
?person
rdf:type
foaf:Person.
?person
foaf:name
?name.
?person
foaf:mbox
?email.
}
SPARQL – example 1
Data:
<http://example.org/book/book1>
<http://purl.org/dc/elements/1.1/title>
"SPARQL Tutorial" .
Query:
SELECT ?title
WHERE
{
<http://example.org/book/book1>
<http://purl.org/dc/elements/1.1/title>
?title .
}
SPARQL – example 2
Data:
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
_:a
_:a
_:b
_:b
_:c
foaf:name
foaf:mbox
foaf:name
foaf:mbox
foaf:mbox
"Johnny Lee Outlaw" .
<mailto:jlow@example.com> .
"Peter Goodguy" .
<mailto:peter@example.org> .
<mailto:carol@example.org> .
SPARQL – example 2
Query:
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name ?mbox
WHERE
{
?x foaf:name ?name .
?x foaf:mbox ?mbox
}
SPARQL – example 2
Result:
name
"Johnny Lee Outlaw“
"Peter Goodguy"
mbox
<mailto:jlow@example.com>
<mailto:peter@example.org>
Construct in SPARQL
Data:
@prefix org: <http://example.com/ns#> .
_:a
org:employeeName
"Alice" .
_:a
org:employeeId
12345 .
_:b
org:employeeName
"Bob" .
_:b
org:employeeId
67890 .
Construct in SPARQL
Query:
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX org: <http://example.com/ns#>
CONSTRUCT
{ ?x foaf:name ?name }
WHERE
{ ?x org:employeeName ?name }
Construct in SPARQL
Result:
@prefix org: <http://example.com/ns#> .
_:x
_:y
foaf:name
foaf:name
"Alice" .
"Bob" .
Construct in SPARQL
Result Serialized:
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:foaf="http://xmlns.com/foaf/0.1/" >
<rdf:Description>
<foaf:name>Alice</foaf:name>
</rdf:Description>
<rdf:Description>
<foaf:name>Bob</foaf:name>
</rdf:Description>
</rdf:RDF>
SPARQL exercise
• Use both SELECT and CONSTRUCT
• What are all the country capitals of Africa?