/**
* tag 'span' of 'doc' according to the Penn Tree Bank tag set. Words are assigned annotations of
* type 'type' with feature cat = a Penn tag.
*/
public void annotate(Document doc, Span span, String type) {
for (int i = 0; i < posTable.length; i++)
tagTable[i] = new String[] {type, "cat", posTable[i], posTable[i]};
annotator = new HMMannotator(posh);
annotator.setTagTable(tagTable);
annotator.setBItag(false);
annotator.setTrace(trace);
annotator.annotateSpan(doc, span);
}
/**
* train the tagger using the DocumentCollection in file 'trainingCollection'.
* 'trainingCollection' should consist of documents which have been explicitly tagged with
* part-of-speech information.
*/
void train(String trainingCollection) {
for (int i = 0; i < posTable.length; i++)
tagTable[i] = new String[] {"constit", "cat", posTable[i], posTable[i]};
// build ergodic HMM with one state for each POS (plus start and end states)
HMMstate startState = new HMMstate("start", "", WordFeatureHMMemitter.class);
posh.addState(startState);
for (int j = 0; j < posTable.length; j++) startState.addArc(new HMMarc(posTable[j], 0));
HMMstate endState = new HMMstate("end", "", WordFeatureHMMemitter.class);
posh.addState(endState);
for (int i = 0; i < posTable.length; i++) {
String pos = posTable[i];
HMMstate state = new HMMstate(pos, pos, WordFeatureHMMemitter.class);
posh.addState(state);
for (int j = 0; j < posTable.length; j++) state.addArc(new HMMarc(posTable[j], 0));
state.addArc(new HMMarc("end", 0));
}
posh.resolveNames();
posh.resetForTraining();
annotator = new HMMannotator(posh);
annotator.setTagTable(tagTable);
annotator.setBItag(false);
DocumentCollection col = new DocumentCollection(trainingCollection);
col.open();
for (int i = 0; i < col.size(); i++) {
ExternalDocument doc = col.get(i);
doc.open();
System.out.println("Training from " + doc.fileName());
// divide at endmarks (constit cat="."), adding "S" marks
int posn = 0;
int start = posn;
Vector anns;
while ((anns = doc.annotationsAt(posn, "constit")) != null) {
Annotation ann = (Annotation) anns.get(0);
posn = ann.span().end();
String pos = (String) ann.get("cat");
if (pos.equals(".")) {
doc.annotate("S", new Span(start, posn), new FeatureSet());
start = posn;
}
}
annotator.train(doc);
// free up space taken by annotations on document
doc.clearAnnotations();
}
posh.computeProbabilities();
}