public String addSkolemConstant()
{
String sc = null;
do
{
sc = "SC" + (skolemConstantIndexical++);
} while (constants.Contains(sc) || functions.Contains(sc)
|| predicates.Contains(sc));
addConstant(sc);
notifyFOLDomainListeners(new FOLDomainSkolemConstantAddedEvent(this, sc));
return sc;
}