Semantically Conditioned LSTM-based Natural Language Generation for Spoken Dialogue Systems
This work addresses the need for more natural and scalable language generation in spoken dialogue systems, representing an incremental improvement over existing methods.
The paper tackled the problem of rigid and unscalable natural language generation in spoken dialogue systems by proposing a semantically controlled LSTM-based generator, which improved performance in objective evaluations and was preferred by human judges for informativeness and naturalness.
Natural language generation (NLG) is a critical component of spoken dialogue and it has a significant impact both on usability and perceived quality. Most NLG systems in common use employ rules and heuristics and tend to generate rigid and stylised responses without the natural variation of human language. They are also not easily scaled to systems covering multiple domains and languages. This paper presents a statistical language generator based on a semantically controlled Long Short-term Memory (LSTM) structure. The LSTM generator can learn from unaligned data by jointly optimising sentence planning and surface realisation using a simple cross entropy training criterion, and language variation can be easily achieved by sampling from output candidates. With fewer heuristics, an objective evaluation in two differing test domains showed the proposed method improved performance compared to previous methods. Human judges scored the LSTM system higher on informativeness and naturalness and overall preferred it to the other systems.