Grounding in dialogue systems

1. Grounding in dialogue systems Staffan Larsson Inst. för lingvistik, GU sl@ling.gu.se OFTI 2002, Göteborg

2. Overview • Background • Interactive Communication Management (ICM) • Action levels and metaissues • Feedback properties • Update strategies • ICM and grounding for a dialogue system

3. Background • Research on dialogue and dialogue systems • TRINDI (1997-2000) • SDS (1997-1998) • SIRIDUS (2000-2002) • D’Homme (2001) • Implementation • TrindiKit: toolkit for building dialogue systems, information state approach • GoDiS: dialogue system; issue-based dialogue management; implemented using TrindiKit

4. GoDiS in SIRIDUS • explore and implement issue-based dialogue management • adapt Ginzburg’s KOS to dialogue system (GoDiS) and implement • extend theory to handle more flexible dialogue (incl. grounding, accommodation, action-oriented dialogue, negotiation, conditional responses) • implement extensions • separating general and domain-dependent phenomena helps reconfigurability • general theory of dialogue • extended into subtheories for different dialogue genres • domain knowledge clearly separated • minimize effort for adapting to new genres and domains

5. T.A. domain knowledge Xerox manual home device manager VCR manager Travel Agency Auto- route inquiry- oriented IBDM action- oriented IBDM GoDiS-I GoDiS-A basic IBDM GoDiS TrindiKit IS approach

6. Basic issue-based dialogue management • dialogue is, basically, all about raising and addressing issues • incl. short answers • issue reraising and accommodation • starting point: KOS framework [Ginzburg] • Dialogue Gameboard (DGB) • related DGB update protocols • dialogue moves: ask, answer, (greet, quit) • other features • dialogue plans • handling multiple simultaneous issues • information sharing between plans • initial genre: enquiry-oriented dialogue (database search) • sample domain: travel agency

7. Interactive Communication Management [Allwood] • feedback • purpose: regulate grounding (adding to common ground) [Clark] • feedback moves reflect grounding status of utterances • turntaking ICM • purpose: regulate turntaking • turntaking moves reflects turntaking structure of dialogue • sequencing • purpose: • coordination of common ground other than grounding • indicating ”internal” mental moves affecting common ground • sequencing moves reflects dialogue structure (part of common ground)

8. Action levels in dialogue [Allwood, Clark] • contact • perception • understanding • acceptance

9. Grounding and action levels • ”To ground a thing … is to establish it as part of common ground well enough for current purposes.” [Clark] • grounding applies to all action levels • not just understanding • U is grounded on level L iff • the grounding issue on level L is positively resolved • grounding assumptions correspond to information state updates in system

10. Feedback polarity [Allwood et al ’91] • polarity: positive, negative • indicating e.g. understanding (+) or lack thereof (-) • eliciting/non-eliciting (evocative/non-evoc.) • whether utterance introduces obligation to respond • Examples • ”What do you mean?” • negative, eliciting • ”Do you mean that the destination is Paris?” • ??negative??, eliciting • ”To Paris.” • positive, non-eliciting • ”Pardon?” • negative, eliciting

11. Form and content of ICM dialogue moves • Form: • declarative: ”I didn’t hear what you said.”; ”The destination city is Paris.” • interrogative: ”What did you say?”; ”Do you want to go to Paris?” • imperative: ”Please repeat your latest utterance!” • elliptical • interrogative: ”Paris?”, ”To Paris or from Paris?” • declarative: ”To Paris.” • Content: • object-level: ”To Paris?”, ”Do you want to go to Paris?” • metalevel: ”Did you mean you want to go to Paris?” • none (except polarity): ”Pardon?”, ”OK”

12. ICM in GoDiS • Grounding moves • all four action levels • simplified polarities • coarse-grained semantics • no detailed account of form; template-based generation • Sequencing moves • reraising issues • loading dialogue plans • question accommodation • Turntaking moves • no account of turntaking moves; strict turntaking enforced

13. Feedback polarities in GoDiS • how far can we get with meta-issues? • we don’t model obligations • all feedback introduces or answers meta-issues • meta-issues may or may not be responded to; system must be able to deal with both • 3 ”polarities”, mutually exclusive • positive: pos • implicitly introduces question such as ”was p a correct interpretation of U?” • negative: neg • answers question such as ”did B understand U?” • eliciting->interrogative: int • explicitly raises question, e.g. ”What does U mean?”

14. Some ICM dialogue moves • feedback • icm:Level{*Polarity}{:Content} • icm:und*neg – ”I don’t understand” • icm:und*pos:P – ”To Paris.” • icm:und*int:Q – ”Did you mean to Paris or from Paris?” • icm:acc*neg:Q – ”Sorry, I can’t answer Q” • icm:acc*pos – ”Okay” • sequencing • icm:Type{:Content} • icm:reraise:Q – ”Returning to the issue Q” • icm:loadplan – ”Let’s see…”

15. System feedback for user utterances • contact • negative (”I didn’t hear anything from you.”, ”hello”) • perception • negative: fb-phrase (”Pardon?”, ”I didn’t hear what you said”) • positive: repetition (”I heard ’to paris’”) • understanding • negative: fb-phrase (”I don’t quite understand”) • positive: reformulation (”To Paris.”) • interrogative: reformulation (”To Paris, is that correct?”, ”To Paris?”) • acceptance/integration • negative: fb-phrase with reformulation (”Sorry, I cannot answer Q”, ”Sorry, Paris is not a valid destination city.”) • positive: fb-word (”Okay.”)

16. User feedback for system utterances • contact: - • perception • negative: fb-phrase (”Pardon?”, ”I didn’t hear what you said”) • understanding: - • acceptance/integration • negative (for questions): fb-phrase (”I don’t know”, ”Never mind”) • positive: fb-word (”okay.”)

17. Grounding update strategies • strategic questions: • When should U assumed to be grounded on level L? • as soon as it has been uttered (of course, the hearer cannot assume grounding until grounding wh-issues have some answer, e.g. ”what did A say?” ) • if B does not give negative feedback • when B gives positive feedback • when B has given eliciting feedback which has been confirmed by A • What to do if the grounding assumption turns out to be mistaken

18. Grounding update strategies cont’d • optimism on level L: • assume U is grounded on level L as soon as U has been uttered • cautious optimism: • make sure the optimistic assumption can easily be retracted • pessimism: • don’t assume U grounded until there has been some positive feedback (or at least no negative feedback)

19. choice of strategies in system • system utterances • optimistically assumed to be grounded on all levels • negative feedback on perception or acceptance levels -> backtrack to saved state • user utterances • if problem on any level, give corresponding negative fb • if several alternatives available, give interrogative fb • if OK on all levels, update strategy and feedback determined by recognition score • S > 0.9 • optimistic update, icm:acc*pos • 0.9 >= S > 0.8 • optimistic update, icm:acc*pos, icm:und*pos:Content • 0.8 >= S >0.5 • pessimistic update, ask(?Content) • if ?Content recieves answer ”yes”, add assume Content grounded

20. S> Welcome to the travel agency! U> price information please S> OK, you want to know about price, is that correct? icm:acc*pos icm:und*int:?issue(price) U> yes S> Lets see. How do you want to travel? U> by flight S> OK, by flight. What city do you want to go to? icm:acc*pos icm:und*pos:means_of_transport(fly) … U> do I need a visa ? … S> Lets see. What country are you from? icm:loadplan U> sweden S> Okay. You are a citizen of Sweden. Yes, you need a Visa. S> Returning to the issue of price… icm:reraise:?x.price(x) … S> What month do you want to leave? U> Don’t know icm:acc*neg …

21. Recommended reading! • Staffan Larsson (2002): Issue-based Dialogue Management. PhD Thesis. • Download the system • www.ling.gu.se/~sl/Thesis • SIRIDUS project • www.ling.gu.se/projekt/siridus

22. rejections • rejection of question Q • inability to answer Q • ”Sorry, I can’t answer that question” • unwillingness to answer Q • ”I don’t want to discuss that” • rejection of proposition as issue • unwillingness to discuss whether ?P • ”I don’t want to discuss that” • other reasons? • rejection of proposition • ”Sorry, I don’t agree.”, ”You’re wrong!”, ”That’s impossible!” • can be expected to lead to argumentation

23. problematic cases S: ”Where do you want to go?” U1: ”Nowhere” U2: ”I don’t know” U3: (silence) OR ”I want first class!” • do these count as rejections? • U1: negative answer? presupposition failiure? rejection? • U2: rejection? • but not as definite as ”No comment!” • U3: rejection? • in any case, irrelevant followup