/**
* This method is used to parse an Assertion in the RuleML Document.
*
* @param ass Element The XOM Element object that represents the assertion.
* @return A term object that represents the assertion in a way that can be used by the reasoning
* engine.
* @throws ParseException Thrown if there is a serious error parsing the assertion.
*/
private Term parseAssert(Element ass) throws ParseException {
Elements children = ass.getChildElements();
Element firstChild = skipRoleTag(children.get(0));
if (firstChild.getLocalName().equals(tagNames.ATOM)) {
DefiniteClause dc = parseFact(firstChild);
Vector<Term> v = new Vector<Term>();
for (int i = 0; i < dc.atoms.length; i++) {
v.add(dc.atoms[i]);
}
Term t = new Term(SymbolTable.IASSERT, SymbolTable.INOROLE, Types.IOBJECT, v);
t.setAtom(true);
return t;
} else if (firstChild.getLocalName().equals(tagNames.IMPLIES)) {
Vector<DefiniteClause> v2 = parseImplies(firstChild);
DefiniteClause dc = (DefiniteClause) v2.get(0);
Vector<Term> v = new Vector<Term>();
for (int i = 0; i < dc.atoms.length; i++) {
v.add(dc.atoms[i]);
}
Term t = new Term(SymbolTable.IASSERT, SymbolTable.INOROLE, Types.IOBJECT, v);
t.setAtom(true);
return t;
} else {
throw new ParseException("Assert element can only contain Atom (fact) or Implies elements.");
}
}
/**
* Method to parse a naf (Negation as Failure)
*
* @param naf Element The XOM element that represents the naf atom to be parsed.
* @return Returns the data structure that represents the naf in a way that can be used by the
* reasoning engine.
* @throws ParseException Thrown if there is an error parsing the naf.
*/
private Term parseNaf(Element naf) throws ParseException {
Elements children = naf.getChildElements();
Element el = skipRoleTag(children.get(0));
Vector<Term> subterms = new Vector<Term>();
if (el.getLocalName().equals(tagNames.ATOM)) {
subterms.add(parseAtom(el, false, false));
} else if (el.getLocalName().equals(tagNames.AND)) {
children = el.getChildElements();
for (int i = 0; i < children.size(); i++) {
Element el2 = children.get(i);
if (!el2.getLocalName().equals(tagNames.ATOM)) {
throw new ParseException("And child of Naf element should only contain Atom elements.");
}
subterms.add(parseAtom(el2, false, false));
}
} else {
throw new ParseException("Naf element should only contain Atom or And child element.");
}
Term t = new Term(SymbolTable.INAF, SymbolTable.INOROLE, Types.IOBJECT, subterms);
t.setAtom(true);
return t;
}
public DefiniteClause buildResult(Term t) {
if (t.getSymbol() != sym) {
return null;
}
if (t.subTerms.length != 3) {
return null;
}
Term p1 = t.subTerms[1].deepCopy();
Term p2 = t.subTerms[2].deepCopy();
if (p1.getSymbol() < 0 || p2.getSymbol() < 0) {
return null;
}
String p1s = p1.getSymbolString();
String p2s = p2.getSymbolString();
if ((p1.getType() == Types.IFLOAT || p1.getType() == Types.IINTEGER)
&& (p2.getType() == Types.IFLOAT || p2.getType() == Types.IINTEGER)) {
double d1;
double d2;
try {
d1 = Double.parseDouble(p1s);
d2 = Double.parseDouble(p2s);
} catch (Exception e) {
return null;
}
if (d1 > d2) {
return null;
}
} else if (p1.getType() == Types.ISTRING && p2.getType() == Types.ISTRING) {
if (p1s.compareTo(p2s) > 0) {
return null;
}
} else {
return null;
}
Term roid =
new Term(
SymbolTable.internSymbol("$jdrew-lte-" + p1s + "<=" + p2s),
SymbolTable.IOID,
Types.ITHING);
Vector v = new Vector();
v.add(roid);
v.add(p1);
v.add(p2);
Term atm = new Term(sym, SymbolTable.INOROLE, Types.IOBJECT, v);
atm.setAtom(true);
Vector v2 = new Vector();
v2.add(atm);
return new DefiniteClause(v2, new Vector());
}
public DefiniteClause buildResult(Term t) {
if (t.getSymbol() != symbol) {
return null;
}
if (t.subTerms.length != 3) {
return null;
}
Term p2 = t.subTerms[2].deepCopy();
if (p2.getSymbol() < 0) {
return null;
}
if (p2.getType() != Types.IFLOAT && p2.getType() != Types.IINTEGER) {
return null;
}
String p2s = p2.getSymbolString();
double p2d;
try {
p2d = Double.parseDouble(p2s);
} catch (Exception e) {
return null;
}
double result = Math.tan(p2d);
String results = "" + result;
Term r1 = new Term(SymbolTable.internSymbol(results), SymbolTable.INOROLE, Types.IFLOAT);
Term roid =
new Term(SymbolTable.internSymbol("$jdrew-tan-" + p2s), SymbolTable.IOID, Types.ITHING);
Vector v = new Vector();
v.add(roid);
v.add(r1);
v.add(p2);
Term atm = new Term(symbol, SymbolTable.INOROLE, Types.IOBJECT, v);
atm.setAtom(true);
Vector v2 = new Vector();
v2.add(atm);
return new DefiniteClause(v2, new Vector());
}
/**
* Method to parse an Atom
*
* @param Atom Element The XOM element that represents the Atom to be parsed.
* @param head boolean This tells the engine if the atom is a head of a rule.
* @param neg boolean This tells the engine if the atom is a negative atom (Neg)
* @return Returns the data structure that represents the Atom in a way that can be used by the
* reasoning engine.
* @throws ParseException Thrown if there is an error parsing the Atom.
*/
private Term parseAtom(Element atom, boolean head, boolean neg) throws ParseException {
boolean foundoid = false;
Elements children = atom.getChildElements();
// checking for op tag before the rel
Element op = getFirstChildElement(atom, tagNames.OP);
Element rel = null;
if (op != null) {
Elements relTag = op.getChildElements();
rel = relTag.get(0);
} else {
rel = getFirstChildElement(atom, tagNames.REL);
}
if (rel == null) {
throw new ParseException("In an <Atom>, first child of <op> must be a <Rel>.");
}
String relname = rel.getValue().trim();
if (neg) {
relname = "$neg-" + relname;
}
int symbol = SymbolTable.internSymbol(relname);
Vector<Term> subterms = new Vector<Term>();
int startIndex = getFirstChildElementIndex(children, 0) + 1;
for (int i = startIndex; i < children.size(); i++) {
Element element = children.get(i);
Term term = null;
if (element.getLocalName().equals(tagNames.OID)) {
if (foundoid) {
throw new ParseException("<Atom> must contain a most one <oid>.");
}
term = parseOid(element);
foundoid = true;
} else {
term = parseDefaultElement(element);
}
subterms.add(term);
}
// Generate a fake OID if the atom does not have one.
// This is a requirement put in place by the reasoner.
if (!foundoid) {
if (head) {
String symname = "$gensym" + SymbolTable.genid++;
int symid = SymbolTable.internSymbol(symname);
Term t2 = new Term(symid, SymbolTable.IOID, Types.IOBJECT);
subterms.add(t2);
} else {
String varname = generateAnonymousIdentifier();
int symid = this.internVariable(varname);
Vector<Integer> types = new Vector<Integer>();
types.add(Types.IOBJECT);
this.varClasses.put(symid, types);
Term t2 = new Term(symid, SymbolTable.IOID, Types.IOBJECT);
subterms.add(t2);
}
}
Term t = new Term(symbol, SymbolTable.INOROLE, Types.IOBJECT, subterms);
t.setAtom(true);
return t;
}
