/**
* Unifies this feature map with another feature map. Two feature maps can unify if and only if
* all values of common feature name unify. If the unification fails, a UnificationFailedException
* is thrown. In this case, the two feature maps remain partly unified, i.e. no backtracking is
* done. Thus, this operation should be perfomed only if it is certain that the unification
* succeeds, or if the operation is performed on copies of objects that are not used anymore
* afterwards.
*
* @param featureMap The feature map to be unified with this feature map.
* @throws UnificationFailedException If unification fails.
*/
public void unify(FeatureMap featureMap) throws UnificationFailedException {
for (String f : features.keySet()) {
getFeature(f).unify(featureMap.getFeature(f));
}
for (String f : featureMap.features.keySet()) {
getFeature(f).unify(featureMap.getFeature(f));
}
}
/**
* This method detects whether this feature map can unify with the given feature map. Neither of
* the two feature maps are changed.
*
* @param featureMap The feature map for the unification check.
* @return true if the two feature map can unify.
*/
public boolean canUnify(FeatureMap featureMap) {
if (!isSimilar(featureMap)) return false;
FeatureMap thisC = deepCopy();
FeatureMap otherC = featureMap.deepCopy();
try {
thisC.tryToUnify(otherC);
} catch (UnificationFailedException ex) {
return false;
}
return true;
}
/**
* Creates a deep copy of this feature map using the given string objects. This method is usually
* called form another deepCopy-method.
*
* @param stringObjs The string objects to be used.
* @return A deep copy.
*/
FeatureMap deepCopy(HashMap<Integer, StringObject> stringObjs) {
FeatureMap fm = new FeatureMap();
for (String feature : features.keySet()) {
StringRef s = features.get(feature);
StringObject se = stringObjs.get(s.getID());
if (se != null) {
fm.setFeature(feature, se.newStringRef());
} else {
StringRef sr = new StringRef(s.getString());
fm.setFeature(feature, sr);
stringObjs.put(s.getID(), sr.getStringObject());
}
}
return fm;
}
/**
* Tries to unify this feature map with another feature map. If unification is not possible, an
* exception is thrown. In the case unification would be possible, the unification is not
* performed completely. In any case the two feature maps remain in an unconsistent state
* afterwards. Thus, this operation should be performed only on copies of objects that are not
* used anymore afterwards.
*
* @param featureMap The feature map to be unified with this feature map.
* @throws UnificationFailedException If unification fails.
*/
public void tryToUnify(FeatureMap featureMap) throws UnificationFailedException {
if (featureMap == null) {
throw new UnificationFailedException();
}
for (String f : features.keySet()) {
features.get(f).unify(featureMap.getFeature(f));
}
}