Introduce naive fresh variable generator

1 files changed, 29 insertions, 25 deletions

diff --git a/src/main/scala/rsacomb/RDFoxAxiomConverter.scala b/src/main/scala/rsacomb/RDFoxAxiomConverter.scala
index 0a79823..d90c966 100644
--- a/src/main/scala/rsacomb/RDFoxAxiomConverter.scala
+++ b/src/main/scala/rsacomb/RDFoxAxiomConverter.scala
@@ -1,6 +1,11 @@
 package rsacomb
 
-import org.semanticweb.owlapi.model.{OWLAxiom, OWLSubClassOfAxiom, OWLEquivalentClassesAxiom, OWLObjectPropertyExpression}
+import org.semanticweb.owlapi.model.{
+  OWLAxiom,
+  OWLSubClassOfAxiom,
+  OWLEquivalentClassesAxiom,
+  OWLObjectPropertyExpression
+}
 import org.semanticweb.owlapi.model.OWLAxiomVisitorEx
 
 import tech.oxfordsemantic.jrdfox.logic.{Rule, BodyFormula}
@@ -17,22 +22,24 @@ import org.semanticweb.owlapi.model.OWLObjectProperty
 object RDFoxAxiomConverter {
 
   def apply(
-    term : Term = Variable.create("x"),
-    skolem : SkolemStrategy = SkolemStrategy.None,
-    unsafe : List[OWLObjectPropertyExpression] = List()
-  ) : RDFoxAxiomConverter =
-          new RDFoxAxiomConverter(term, skolem, unsafe)
+      term: Term,
+      skolem: SkolemStrategy = SkolemStrategy.None,
+      unsafe: List[OWLObjectPropertyExpression] = List()
+  ): RDFoxAxiomConverter =
+    new RDFoxAxiomConverter(term, skolem, unsafe)
 
 } // object RDFoxAxiomConverter
 
-class RDFoxAxiomConverter(term : Term, skolem : SkolemStrategy, unsafe : List[OWLObjectPropertyExpression])
-  extends OWLAxiomVisitorEx[List[Rule]]
-{
+class RDFoxAxiomConverter(
+    term: Term,
+    skolem: SkolemStrategy,
+    unsafe: List[OWLObjectPropertyExpression]
+) extends OWLAxiomVisitorEx[List[Rule]] {
 
-  override
-  def visit(axiom : OWLSubClassOfAxiom) : List[Rule] = {
+  override def visit(axiom: OWLSubClassOfAxiom): List[Rule] = {
     // Skolemization is needed only for the head of an axiom
-    val subVisitor = new RDFoxClassExprConverter(term,SkolemStrategy.None, unsafe)
+    val subVisitor =
+      new RDFoxClassExprConverter(term, SkolemStrategy.None, unsafe)
     val superVisitor = new RDFoxClassExprConverter(term, skolem, unsafe)
     // Each visitor returns a `RDFoxRuleShards`, a tuple (res,ext):
     // - the `res` List is a list of atoms resulting from the conversion
@@ -45,30 +52,27 @@ class RDFoxAxiomConverter(term : Term, skolem : SkolemStrategy, unsafe : List[OW
     val sup = axiom.getSuperClass.accept(superVisitor)
     val head = sup.res.asJava
     val body = (sub.res ++ sup.ext).asJava
-    List(Rule.create(head,body))
+    List(Rule.create(head, body))
   }
 
-  override
-  def visit(axiom : OWLEquivalentClassesAxiom) : List[Rule] = {
+  override def visit(axiom: OWLEquivalentClassesAxiom): List[Rule] = {
     for {
       axiom1 <- axiom.asPairwiseAxioms.asScala.toList
       axiom2 <- axiom1.asOWLSubClassOfAxioms.asScala.toList
-      rule   <- axiom2.accept(this)
+      rule <- axiom2.accept(this)
     } yield rule
   }
 
-  override
-  def visit(axiom : OWLSubObjectPropertyOfAxiom) : List[Rule] = {
-    // TODO: variables needs to be handled at visitor level. Hardcoding
-    // the name of the varibles might lead to errors for complex cases.
-    val term1 = Variable.create("y")
-    val subVisitor = new RDFoxPropertyExprConverter(term,term1,SkolemStrategy.None)
-    val superVisitor = new RDFoxPropertyExprConverter(term,term1,skolem)
+  override def visit(axiom: OWLSubObjectPropertyOfAxiom): List[Rule] = {
+    val term1 = RSA.getFreshVariable()
+    val subVisitor =
+      new RDFoxPropertyExprConverter(term, term1, SkolemStrategy.None)
+    val superVisitor = new RDFoxPropertyExprConverter(term, term1, skolem)
     val body: List[BodyFormula] = axiom.getSubProperty.accept(subVisitor)
     val head: List[Atom] = axiom.getSuperProperty.accept(superVisitor)
-    List(Rule.create(head.asJava,body.asJava))
+    List(Rule.create(head.asJava, body.asJava))
   }
 
-  def doDefault(axiom : OWLAxiom) : List[Rule] = List()
+  def doDefault(axiom: OWLAxiom): List[Rule] = List()
 
 } // class RDFoxAxiomConverter