sis Sproat  Olive ELVIS uses only TTS since it would not be possible to pre record and then concatenate  all the words necessary for realizing the content of email messages The spoken language understanding SLU module consists of a set of rules for specifying the vocabulary and allowable utterances  and an associated set of rules for translating the user s utterance into a domain specific semantic representation of its meaning   The syntactic rules are converted into an FSM network that is used directly by the speech recognizer Mohri Pereira The semantic rule that is associated with each syntactic Riley rule maps the user s utterance directly to an application specific template consisting of an application function name and its arguments These templates are then converted directly to application specific function calls specified in the application module  The understanding module also supports dynamic grammar generation and loading because the recognizer vocabulary must change during the interaction eg to support selection of email messages by content fields such as sender and subject The application module provides application specific functions  e g   functions for access ing message attributes such as subject and sender  and functions for making these realizable as speech so that they can be used to instantiate variables in spoken language generation

## Elvis S Dialogue Manager And Strategies

ELVIS s dialogue manager is based on a state machine where one or more dialogue strategies can be explored in each state The state of the dialogue manager is defined by a set of state variables representing various items of information that the dialogue manager uses in deciding what to do next The state variables encode various observations of the user s conversational behavior  such as the results of processing the user s speech with the spoken language understanding  SLU  module  and results from accessing information databases relevant to the application as well as certain aspects of the dialogue history A dialogue strategy is a specification of what the system should say  in ELVIS this is represented as a template with variables that must be instantiated by the current context In some states the ssssem always executes the same dialogue strategy and in other states alternate strategies are explored  All of the strategies implemented in ELVIS are summarized in Figure complete specification of which dialogue strategy should be executed in each state is called a policy for a dialogue system To develop a version of ELVIS that supported exploring a number of possible policies we implemented several different choices in particular states of the system  Our goal was to implement strategy choices in states where the optimal strategy was not obvious a priori For the purpose of illustrating the dialogue strategies we explored  consider a situation in which the user is attempting to execute the following task  one of the tasks used in the experimental data collection described in Section You are working at home in the morning and plan to go directly to a meeting
- Task when you go into work  Kim said she would send you a message telling you where and when the meeting is  Find out the Meeting Time and the Meeting Place To complete this task the user needs to find a message from Kim about a meeting in her inbox and listen to it  There are many possible strategies that ELVIS could use to help the user accomplish this task  Below  we first describe the dialogue strategies from Figure