public Variable lookupVariable(String id) {
		/*
		 * A variable lookup can only occur inside a method or a class.
		 * Everything else is invalid.
		 */
		/*
		 * TODO: improve this hack!
		 */
		Variable variable;
		Scopeable currentScope = this.currentScope();
		Scopeable outerScope = this.currentScope().getOuterScope();

		if((variable = currentScope.lookupVariable(id)) != null){ // check local scope
			return variable;
		} else if(outerScope != null) { // check class scope / outer scope
			Identifier classId;
			if((variable = outerScope.lookupVariable(id)) != null) {
				return variable;
			} else if(outerScope.isClass() &&  (classId = outerScope.getId()) != null) { // check parent class scope
				Klass klass = this.globalScope().lookupClass(classId.toString());
				Klass derivedClass;
				if(klass.isDerived() && (derivedClass = this.globalScope().lookupClass(klass.getDerivedId())) != null) {
					if((variable = derivedClass.lookupVariable(id)) != null) {
						return variable;
					}
				}
			}
		}
		return null;
	}