public AnnotationDB search(AnnotationType at) {
    Set hits = new HashSet();

    for (Iterator i = anns.iterator(); i.hasNext(); ) {
      Annotation ann = (Annotation) i.next();
      hits.addAll(AnnotationTools.searchAnnotation(ann, at));
    }

    if (hits.isEmpty()) {
      return AnnotationDB.EMPTY;
    } else {
      return new SimpleAnnotationDB("", hits, at);
    }
  }