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SPARQL with RDFS Entailment - Reasoning Exercises

Introduction

In previous exercises, we wrote SPARQL queries against explicit RDF triples. But one of the most powerful features of semantic technologies is reasoning — the ability to infer new knowledge from existing data using logical rules.

RDFS (RDF Schema) provides basic reasoning capabilities through:

  • Class hierarchies (rdfs:subClassOf)
  • Property domains and ranges (rdfs:domain, rdfs:range)
  • Property hierarchies (rdfs:subPropertyOf)

This exercise demonstrates how RDFS reasoning makes queries simpler and more powerful.

Setup: The Ontology

First, we need to define our ontology with RDFS statements that describe the structure of our domain.

ontology.ttl

<http://www.example.com/Room> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2000/01/rdf-schema#Class> .
<http://www.example.com/Room> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2002/07/owl#Class> .
<http://www.example.com/Room> <http://www.w3.org/2000/01/rdf-schema#label> "Room" .
<http://www.example.com/Room> <http://www.w3.org/2000/01/rdf-schema#comment> "A hospital room" .

<http://www.example.com/Patient> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2000/01/rdf-schema#Class> .
<http://www.example.com/Patient> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2002/07/owl#Class> .
<http://www.example.com/Patient> <http://www.w3.org/2000/01/rdf-schema#label> "Patient" .
<http://www.example.com/Patient> <http://www.w3.org/2000/01/rdf-schema#comment> "A hospital patient" .
  
<http://www.example.com/HighRiskPatient> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2000/01/rdf-schema#Class> .
<http://www.example.com/HighRiskPatient> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2002/07/owl#Class> .
<http://www.example.com/HighRiskPatient> <http://www.w3.org/2000/01/rdf-schema#label> "High Risk Patient" .
<http://www.example.com/HighRiskPatient> <http://www.w3.org/2000/01/rdf-schema#subClassOf> <http://www.example.com/Patient> .
<http://www.example.com/HighRiskPatient> <http://www.w3.org/2000/01/rdf-schema#comment> "Patient with elevated risk factors" .

<http://www.example.com/Nurse> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2000/01/rdf-schema#Class> .
<http://www.example.com/Nurse> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2002/07/owl#Class> .
<http://www.example.com/Nurse> <http://www.w3.org/2000/01/rdf-schema#label> "Nurse" .
<http://www.example.com/Nurse> <http://www.w3.org/2000/01/rdf-schema#comment> "A healthcare nurse" .

<http://www.example.com/locatedIn> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/1999/02/22-rdf-syntax-ns#Property> .
<http://www.example.com/locatedIn> <http://www.w3.org/2000/01/rdf-schema#label> "located in" .
<http://www.example.com/locatedIn> <http://www.w3.org/2000/01/rdf-schema#domain> <http://www.example.com/Patient> .
<http://www.example.com/locatedIn> <http://www.w3.org/2000/01/rdf-schema#range> <http://www.example.com/Room> .
<http://www.example.com/locatedIn> <http://www.w3.org/2000/01/rdf-schema#comment> "Patient is located in a room" .

<http://www.example.com/assignedTo> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/1999/02/22-rdf-syntax-ns#Property> .
<http://www.example.com/assignedTo> <http://www.w3.org/2000/01/rdf-schema#label> "assigned to" .
<http://www.example.com/assignedTo> <http://www.w3.org/2000/01/rdf-schema#domain> <http://www.example.com/Patient> .
<http://www.example.com/assignedTo> <http://www.w3.org/2000/01/rdf-schema#range> <http://www.example.com/Nurse> .
<http://www.example.com/assignedTo> <http://www.w3.org/2000/01/rdf-schema#comment> "Patient is assigned to a nurse" .

<http://www.example.com/patient1> <http://www.example.com/assignedTo> <http://www.example.com/nurse1> .
<http://www.example.com/patient2> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.example.com/HighRiskPatient> .  
<http://www.example.com/patient3> <http://www.example.com/locatedIn> <http://www.example.com/room1> .

The Challenge: Querying with Class Hierarchies and domain/range definitions

Question: "Find all patients"

Note that there are no explicit patient definitions.

Exercise: Query With Reasoning

What the Reasoner Infers

When RDFS reasoning is enabled, the reasoner automatically infers additional triples based on rdfs:subClassOf and rdfs:domain / rdfs:range statements:

From the ontology:

example:HighRiskPatient rdfs:subClassOf example:Patient .

example:assignedTo rdfs:domain example:Patient .
example:assignedTo rdfs:range example:Nurse .

example:locatedIn rdfs:domain example:Patient .
example:locatedIn rdfs:range example:Room .

And data:

example:patient1 example:assignedTo example:nurse1 .
example:patient2 a example:HighRiskPatient .  
example:patient3 example:locatedIn example:room1 .

Your Task

Now write RDFS rules to support subClassOf, domain and range definitions.

PREFIX example: <http://www.example.com/>

SELECT *
WHERE {
  ?patient a example:Patient.
}

Rules in Kolibrie follow the syntex:

RULE :SomeRuleName:- 
CONSTRUCT { 
   ?s a :Head.

}
WHERE { 
   ?s a :Body.
}

As a starting point, the rule in Kolibrie syntax to write the subclassOf rule is

RULE :RDFS9:- 
CONSTRUCT { 
   ?p a ?s.

}
WHERE { 
   ?c <http://www.w3.org/2000/01/rdf-schema#subClassOf> ?s.
   ?p <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?c .
}

RDFS Rule 2 — rdfs:domain

Premise
ppp <http://www.w3.org/2000/01/rdf-schema#domain> zzz .
uuu ppp yyy .
Conclusion
uuu a zzz .

In plain English: if a property has a declared domain, then any subject that uses that property is inferred to be an instance of that domain class.

Example

ex:located_in rdfs:domain ex:Patient .

ex:patient1 ex:located_in ex:room1 .

Inferred:

ex:patient1 rdf:type ex:Patient .   # via rdfs2

RDFS Rule 3 — rdfs:range

Premise
ppp <http://www.w3.org/2000/01/rdf-schema#range> zzz .
uuu ppp vvv .
Conclusion
vvv a zzz .

In plain English: if a property has a declared range, then any object that appears as the value of that property is inferred to be an instance of that range class.

Example

ex:located_in rdfs:range ex:Room .

ex:patient1 ex:located_in ex:room1 .

Inferred:

ex:room1 rdf:type ex:Room .         # via rdfs3