Semi-Supervised Learning of Statistical Models for Natural Language Understanding

Table 1

Abstract semantic annotation and its flattened semantic tag sequence.

Sentence	I want to return to Dallas on Thursday.
Annotation	RETURN (TOLOC (CITY (Dallas)) ON (DATE (Thursday)))
(a) Flattened semantic tag list:
RETURN RETURN+TOLOC RETURN+TOLOC+CITY (Dallas) RETURN+ON RETURN+ON+DATE (Thursday)
(b) Expanded semantic tag list:
RETURN RETURN+DUMMY RETURN+TOLOC RETURN+TOLOC+DUMMY RETURN+TOLOC+CITY (Dallas)
RETURN+ON RETURN+ON+DUMMY RETURN+ON+DATE (Thursday) RETURN+ON+DATE (Thursday)+DUMMY