Due to the difficulty in deep semantic parsing, most of previous work focuses on shallow semantic parsing, which assigns a simple structure (such as WHO did WHAT to WHOM, WHEN, WHERE, WHY, HOW) to each predicate in a sentence.
the well-defined semantic role labeling (SRL) task has been drawing more and more attention in recent years due to its importance in deep NLP applications, such as question answering (Narayanan and Harabagiu, 2004), information extraction (Surdeanu et al., 2003), and co-reference resolution (Ponzetto and Strube, 2006).