Introduction

In addition to RDFS++ reasoning, AllegroGraph also supports reasoning over hasValue restrictions in equivalent classes or subclasses.

For example, here is an owl class definition for AtlantisMission, defined as a SpaceMission where the shuttleUsed property has the value Atlantis.

<owl:Class rdf:ID="AtlantisMission">  
    <rdfs:subClassOf  
        rdf:resource="http://www.w3.org/2002/07/owl#Thing"/>  
    <rdfs:label  
        rdf:datatype="http://www.w3.org/2001/XMLSchema#string">  
        Atlantis mission  
    </rdfs:label>  
    <owl:equivalentClass>  
        <owl:Class>  
            <owl:intersectionOf rdf:parseType="Collection">  
            <rdf:Description rdf:ID="SpaceMission"/>  
            <owl:Restriction>  
                <owl:onProperty rdf:resource="#shuttleUsed"/>  
                <owl:hasValue rdf:resource="#Atlantis"/>  
            </owl:Restriction>  
            </owl:intersectionOf>  
        </owl:Class>  
    </owl:equivalentClass>  
</owl:Class>  

We can make two types of inferences from this definition.

1. We can derive the default value for shuttleUsed when we have an Instance of an AtlantisMission. For example, if a triple-store contains the the ontology definition above and we add the following triple:

   (add-triple  
    !m:Mission4 !rdf:type !m:AtlantisMission) 

then we can derive that the shuttleUsed property must be Atlantis with the following query.

(select (?val)  
  (q !m:Mission3 !m:shuttleUsed ?val)) 

2. The reasoning also works in reverse: we can derive the type of an instance to be an AtlantisMission if it has the right properties. If we added the following instance properties to a triple-store

   (add-triple  
     !m:Mission5 !m:shuttleUsed !m:Atlantis)    
   (add-triple  
     !m:Mission5 !rdf:type !m:SpaceMission) 

then the following query would derive that ?x is an AtlantisMission.

(select (?x)  
  (q !m:Mission5 !rdf:type ?x)) 

hasValue reasoning is not enabled by default. The tutorial below will show how to turn this on.

How to use hasValue reasoning

From Java

See the description of setEntailmentRegime.

From Python

On any Python API where infer or includeInferred is an argument, the values can be the boolean False (which means no reasoning), True, which is the same as "rdfs++", or the strings "rdfs++" (rdf++ reasoning but not hasValue reasoning) or "restriction" ("restriction" turns on hasValue reasoning as well as rdf++ reasoning).

From HTTP

Set the infer parameter to restriction when using the repository interface of the HTTP protocol.

How to use it from Lisp: a tutorial

In principle the following code will all run. Just evaluate every expression from top to bottom and you will see the results.

; load agraph into lisp  
(require :agraph)  
 
; go into the triple-store-user package  
(in-package :triple-store-user)  
 
;; make it easier to type URIs  
(enable-!-reader) 

The following will define the function to load the files SpaceMissions2.ntriples into the triple-store. This file is included in the distribution. It will help you understanding of the contents of this file to inspect it in TopBraid Composer.

(defun read-sm ()  
  (create-triple-store  "test11")  
  (load-ntriples "sys:agraph;tutorial-files;SpaceMissions2.ntriples"))  
 
(time (read-sm))                  ; do the actual read 

We are lazy and don't want to type long namespaces:

(register-namespace  
  "m" "http://www.topbraid.org/spacemissions.owl#")  
 
;; lets look at the triples..  
(print-triples *db* :limit nil :format :terse) 

To use restriction reasoning, we must either apply-rdfs++-reasoner and then use restriction-reasoning-enabled-p or use the initarg.

(apply-rdfs++-reasoner)  
(setf (restriction-reasoning-enabled-p *db*) t) 

or

(apply-rdfs++-reasoner :restriction-reasoning-enabled t) 

Deriving default values from type information

1. First we demonstrate how we to derive default values from type information

   (add-triple  
     !m:Mission1 !rdf:type !m:SpaceMissionIn2000)  
   (add-triple  
     !m:Mission1 !m:added-by !m:Jans)  
    
   (select (?x ?y)  
     (q !m:Mission1 !m:startYear ?x)  
     (q- !m:Mission1 !m:added-by ?y)) 

and some more examples:

(add-triple  
   !m:Mission3 !rdf:type !m:DiscoveryMission)  
(add-triple  
   !m:Mission4 !rdf:type !m:AtlantisMission)  
 
(select (?val)  
  (q !m:Mission3 !m:shuttleUsed ?val))  
 
(select (?val)  
  (q !m:Mission4 !m:shuttleUsed ?val))  
 
(select ()  
  (q !m:Mission4 !m:shuttleUsed !m:Atlantis)  
  (write 'SUCCESS)) 

Deriving types from value information

1. Second, we demo how we can derive types from values. We add the shuttleUsed property to Mission5 and then we can automatically derive that Mission5 is an AtlantisMission.

   (add-triple  
     !m:Mission5 !m:shuttleUsed !m:Atlantis) 

Now this select query returns two results:

(select (?x)  
  (q !m:Mission5 !rdf:type ?x))  
 
(("http://www.topbraid.org/spacemissions.owl#SpaceMission")  
 ("http://www.topbraid.org/spacemissions.owl#AtlantisMission")) 

The first result is due to the fact that the rdfs:range of the property shuttleUsed is 'SpaceMission'. So by adding the fact shuttleUsed to Mission5 the RDFS++ range reasoning will derive that Mission5 is a SpaceMission.

Then the restriction reasoning module uses the fact that Misison5 is a SpaceMission and the shuttleUsed is Atlantis to derive that Mission5 is an AtlantisMission.

The following queries are also interesting. The first select will only return Mission4 because we use q- and q- looks only at the ground triples. It returns Mission4 because we added that triple above:

(select (?x)  
  (q- ?x !rdf:type !m:AtlantisMission))  
-> (("http://www.topbraid.org/spacemissions.owl#Mission4")) 

The following query returns Mission4 and also Mission5 because of hasValue reasoning. (Note how we use q here to use the reasoner)

(select (?x)  
  (q ?x !rdf:type !m:AtlantisMission))  
->  
(("http://www.topbraid.org/spacemissions.owl#Mission4")  
 ("http://www.topbraid.org/spacemissions.owl#Mission5"))   

Now we can add some more triples:

(add-triple !m:Mission6 !m:shuttleUsed !m:Columbia)  
(add-triple !m:Mission6 !rdf:type !m:SpaceMission)  
 
(select (?x)  
  (q !m:Mission6 !rdf:type ?x))  
 
(select (?x)  
  (q ?x !rdf:type !m:DiscoveryMission))  
 
(select ()  
  (q !m:Mission6 !rdf:type !m:DiscoveryMission)  
  (lisp (print 'SUCCESS)))  

And finally we show that we can do quite complex hasValue restrictions. Please look in TopBraidComposer or any other ontology browser how a MilitarySpaceMission is defined by multiple hasValue restrictions.

We add some values and everything should work.

(add-triple !m:Mission7 !rdf:type !m:SpaceMission)  
(add-triple !m:Mission7 !m:hasMissionType !m:SpecialMissionType)  
(add-triple !m:Mission7 !m:hasMissionType !m:MilitaryMissionType)  
 
(select (?x ?y)  
  (q !m:Mission7 ?x ?y))  
 
(select (?type)  
  (q !m:Mission7 !rdf:type ?type))  
 
(select (?x)  
  (q ?x !rdf:type !m:MilitarySpaceMission))