public boolean verify(KnowledgeBase kb) {
final Map<KnowledgeElement, Boolean> results = new LinkedHashMap<KnowledgeElement, Boolean>();
KnowledgeBaseVisitor visitor =
new AbstractKnowledgeBaseVisitor() {
Collection<Variable> vars = null;
Collection<Variable> varsInBody = new HashSet<Variable>();
Collection<Variable> varsInHead = new ArrayList<Variable>();
DerivationRule context = null;
public boolean visit(DerivationRule r) {
context = r;
varsInHead.clear();
varsInBody.clear();
return true;
}
public void endVisit(DerivationRule r) {
context = null;
Variable var = null;
for (Variable v : varsInHead) {
if (!varsInBody.contains(v)) var = v;
}
if (var == null) reportOK(r);
else reportViolation("variable ", var, " in ", r, " occurs only in rule head");
results.put(r, var == null);
}
public boolean visit(Fact f) {
if (context == null) {
return false;
} else if (context.getHead() == f) {
vars = varsInHead;
} else if (context.getBody().contains(f)) {
vars = varsInBody;
}
return true;
}
public boolean visit(Variable t) {
vars.add(t);
return true;
}
};
kb.accept(visitor);
for (boolean b : results.values()) {
if (!b) return false;
}
return true;
}
