Generating Predictable and Adaptive Dialog Policies in Single- A nd Multi-domain Goal-oriented Dialog Systems

Nhat Le, A. B. Siddique, Fuad Jamour, Samet Oymak, Vagelis Hristidis

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Most existing commercial goal-oriented chatbots are diagram-based; i.e. they follow a rigid dialog flow to fill the slot values needed to achieve a user's goal. Diagram-based chatbots are predictable, thus their adoption in commercial settings; however, their lack of flexibility may cause many users to leave the conversation before achieving their goal. On the other hand, state-of-the-art research chatbots use Reinforcement Learning (RL) to generate flexible dialog policies. However, such chatbots can be unpredictable, may violate the intended business constraints, and require large training datasets to produce a mature policy. We propose a framework that achieves a middle ground between the diagram-based and RL-based chatbots: We constrain the space of possible chatbot responses using a novel structure, the chatbot dependency graph, and use RL to dynamically select the best valid responses. Dependency graphs are directed graphs that conveniently express a chatbot's logic by defining the dependencies among slots: All valid dialog flows are encapsulated in one dependency graph. Our experiments in both single-domain and multi-domain settings show that our framework quickly adapts to user characteristics and achieves up to 23.77% improved success rate compared to a state-of-the-art RL model.

Original languageEnglish
Pages (from-to)419-439
Number of pages21
JournalInternational Journal of Semantic Computing
Issue number4
StatePublished - Dec 1 2021

Bibliographical note

Publisher Copyright:
© 2021 World Scientific Publishing Company.


  • Chatbots
  • dialog policy
  • reinforcement learning

ASJC Scopus subject areas

  • Software
  • Information Systems
  • Linguistics and Language
  • Computer Science Applications
  • Computer Networks and Communications
  • Artificial Intelligence


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