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package rsacomb
import tech.oxfordsemantic.jrdfox.logic.IRI
sealed trait SkolemStrategy
object SkolemStrategy {
// TODO: might want to use something else other than `hashCode` as a
// function to generate a fresh function/constant
/* No skolemization at all.
*
* From
* ∃R.A ⊑ B
* to
* R(x,y), B(y) -> B(x)
*/
case object None extends SkolemStrategy
/* Functional skolemization
*
* From
* A ⊑ ∃R.B
* to
* A(y) -> R(x,f(x)), B(f(x))
* for f, fresh function associated with the input axiom
*/
case class Standard(func: IRI) extends SkolemStrategy
object Standard {
def apply(axiom: String) =
new Standard(IRI.create(genFunctionString(axiom)))
def genFunctionString(str: String) = "f_" ++ str.hashCode.toString
}
/* Constant skolemization
*
* From
* A ⊑ ∃R.B
* to
* A(y) -> R(x,c), B(c)
* for c, fresh constant associated with the input axiom
*/
case class Constant(const: IRI) extends SkolemStrategy
object Constant {
def apply(axiom: String) =
new Constant(IRI.create(genConstantString(axiom)))
def genConstantString(str: String) = "c_" ++ str.hashCode.toString
}
/* (RSA) Constant skolemization
* This is a special skolemization option to introduce additional atoms for RSA
* checking algorithm.
*
* From
* A ⊑ ∃R.B
* to
* A(y) -> R(x,c), PE(x,c), B(c)
* for c, fresh constant associated with the input axiom and PE an internal predicate.
*/
case class ConstantRSA(const: IRI) extends SkolemStrategy
object ConstantRSA {
def apply(axiom: String) =
new ConstantRSA(IRI.create(genConstantString(axiom)))
def genConstantString(str: String) = "c_" ++ str.hashCode.toString
}
}
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