24.5.1 Dialogue Acts
As we implied above, the speech acts as originally defined by Austin don't model key features of conversation such as grounding, contributions, adjacency pairs and so on. In order to capture these conversational phenomena, we use an extension of speech acts called dialogue acts (Bunt, 1994) (or dialogue moves or conversational moves (Power, 1979; Carletta et al., 1997b). A dialogue act extends speech acts with internal structure related specifically to these other conversational functions (Allen and Core, 1997; Bunt, 2000).
A wide variety of dialogue act tagsets have been proposed. Fig. 24.17 shows a very domain-specific tagset for the Verbmobil two-party scheduling domain, in which speakers were asked to plan a meeting at some future date. Notice that it has many very domain-specific tags, such as SUGGEST, used for when someone proposes a particular date to meet, and ACCEPT and REJECT, used to accept or reject a proposal for a date. Thus it has elements both from the presentation and acceptance phases of the Clark contributions discussed on page 7.
| Tag | Example |
| THANK | Thanks |
| GREET | Hello Dan |
| INTRODUCE | It's me again |
| BYE | Allright bye |
| REQUEST-COMMENT | How does that look? |
| SUGGEST | from thirteenth through seventeenth June |
| REJECT | No Friday I'm booked all day |
| ACCEPT | Saturday sounds fine, |
| REQUEST-SUGGEST | What is a good day of the week for you? |
| INIT | I wanted to make an appointment with you |
| GIVE_REASON | Because I have meetings all afternoon |
| FEEDBACK | Okay |
| DELIBERATE | Let me check my calendar here |
| CONFIRM | Okay, that would be wonderful |
| CLARIFY | Okay, do you mean Tuesday the 23rd? |
| DIGRESS | [we could meet for lunch] and eat lots of ice cream |
| MOTIVATE | We should go to visit our subsidiary in Munich |
| GARBAGE | Oops, I- |
There are a number of more general and domain-independent dialogue act tagsets. In the DAMSL (Dialogue Act Markup in Several Layers) architecture inspired by the
| Act type | Sample Acts |
| turn-taking grounding core speech acts argumentation | take-turn, keep-turn, release-turn, assign-turn acknowledge, repair, continue inform, wh-question, accept, request, offer elaborate, summarize, question-answer, clarify |
| Figure 24.18 | Conversation act types, from Traum and Hinkelman (1992). |
work of Clark and Schaefer (1989) and Allwood et al. (1992), Allwood (1995) each utterance is tagged for two functions, forward looking functions like speech act functions, and the backward looking function, like grounding and answering, which ‘look back’ to the interlocutor’s previous utterance (Allen and Core, 1997; Walker et al., 1996; Carletta et al., 1997a; Core et al., 1999).
Traum and Hinkelman (1992) proposed that the core speech acts and grounding acts that constitute dialogue acts could fit into an even richer hierarchy of conversation acts. Fig. 24.18 shows the four levels of act types they propose, with the two middle levels corresponding to DAMSL dialogue acts (grounding and core speech acts). The two new levels include turn-taking acts and argumentation relation, a conversational version of the coherence relations of Ch. 21.
The acts form a hierarchy, in that performance of an act at a higher level (for example a core speech act) entails performance of a lower level act (taking a turn). We will see the use of conversational acts in generation later on in this section, and will return to the question of coherence and dialogue structure in Sec. 24.7.