/**
* Returns the primary thing this sentence is talking about. More precisely: Returns any subject
* or a passive subject of the sentence, or the root if none applies.
*
* @param graph
* @return
*/
public static IndexedWord getSubject(SemanticGraph graph) {
if (graph.isEmpty()) {
return null;
}
GrammaticalRelation[] subjects = {
EnglishGrammaticalRelations.NOMINAL_SUBJECT,
EnglishGrammaticalRelations.NOMINAL_PASSIVE_SUBJECT,
EnglishGrammaticalRelations.CLAUSAL_SUBJECT,
EnglishGrammaticalRelations.CLAUSAL_PASSIVE_SUBJECT
};
IndexedWord firstRoot = graph.getFirstRoot();
List<IndexedWord> children = graph.getChildrenWithRelns(firstRoot, Arrays.asList(subjects));
if (children != null && children.size() > 0) {
assert children.size()
== 1; // not really dangerous. But we need to change our implementation to return a list,
// if there are more than one subject.
return children.get(0);
}
// return null;
return graph.getFirstRoot(); // in a subject-less sentence, the root is as good as the subject
}
