
| Strategy Type                                  | Choices                           | Strategy Choices      |                   |     |
|------------------------------------------------|-----------------------------------|-----------------------|-------------------|-----|
| Explored                                       | Mixed Initiative  MI              |                       |                   |     |
| Initiative                                     | yes                               | System Initiative  SI |                   |     |
| Summarization                                  | yes                               | SummarizeBoth   SB    | SummarizeSystem   | SS  |
| SummarizeChoicePrompt SCP                      |                                   |                       |                   |     |
| Reading                                        | Read First                        | RF                    | Read Summary Only | RSO |
| yes                                            | Read  Choice Prompt   RCP         |                       |                   |     |
| Ask Which Selection                            |                                   |                       |                   |     |
| Request Info                                   | no                                | AskUserName           | AskW S            |     |
| Ask Selection Criteria  AskSC                  |                                   |                       |                   |     |
| Provide Info                                   | no                                | Read Message          |                   |     |
| Help                                           | AskUserName Help    SI Top Help   | MI Top Help           |                   |     |
| no                                             | Read  Message  Help   AskWS  Help | AskSC Help            |                   |     |
| Timeout                                        | no                                | AskUserName Timeout   | Read Timeout      |     |
| SI Top Timeout  MI Top Timeout  Read Message   |                                   |                       |                   |     |
| Timeout  AskWS Timeout  AskSC Timeout          |                                   |                       |                   |     |
| Rejection                                      | AskUserName Reject                |                       |                   |     |
| no                                             | SI                                |                       |                   |     |
| Top Reject  MI Top Reject  AskWS Reject  AskSC |                                   |                       |                   |     |
| Reject  Read Message Reject                    |                                   |                       |                   |     |

Figure ELVIS s Dialogue Strategies   ELVIS explores choices in Initiative   Summarization and Read Strategies and uses fixed strategies elsewhere that Elvis makes choices among then describe in detail the complete state machine the dialogue strategies from Figure that are used in states where there is no choice among dialogue strategies  and the space of policies that ELVIS can execute  We provide several detailed examples of dialogues that can be generated by ELVIS s dialogue manager s state machine

## 2.1.1 Strategy Choices In Elvis

One strategy choice in our experiments involved the exploration of two different strategies for managing the dialogue initiative system initiative and mixed initiative In the imple mentation of ELVIS tested here  the choice of initiative was made early in the dialogue and the same style of initiative was then used throughout the dialogue whenever there could have been a choice between the two in order to avoid confusing the user Previous research suggested that the system initiative strategy in Figure in which ELVIS is directive with the user might be the best strategy given the current state of the In Figure art in speech recognition  Kamm each of ELVISs utterances is labelled with the name of the dialogue strategy that ELVIS is using to produce the utterance  e g utterance E  is labelled SI Top  the name for the system initiative top level strategy  The choice of the system initiative strategy also affects utterances E and E in these utterances ELVIS continues the dialogue by requesting particular items of information  In general  the ssssem initiative strategy constrains what the user can say at each point in the dialogue by requesting particular items of information one at a time  and the user is constrained to only providing the information that has been asked for  The reason why this strategy is recommended given the current state of the art in speech recognition is that it guides the