Pragmatic And Grammatical Aspects Of The Development Of Dialogue Strategies

James Monaghan

Linguistics, University of Hertfordshire, Hatfield, Herts, England 
linqjm@herts.ac.uk

	Abstract. Technological developments in telephone-based dialogue systems have 	led to a situation where the main hindrance to progress is our lack of understanding 	of how dialogues work. The challenge to us is to understand dialogues in order to 	design efficient automated systems which take account of what users instinctively 	need.  Two areas are addressed. Firstly, there is the fact that users automatically 	relate to the interpersonal aspect of each others participant role.  The other one is 	that dialogue sequences are joint productions and grammatical expectations are 	exchanged in a way not immediately intuitive to the observer.  Examples are 	presented and possible ways forward discussed

1  Introduction

The current increase in the use and availability of telecomms-based information systems is largely technology-driven and as a result has thrown up many problems at the user interface.  Speech interfaces, hand-held display systems, whether text or graphics-based, speed of accessing and processing information have all improved exponentially in availability as well as in reliability.

A case in point is automatic speech recognition.  This has been possible for over forty years but it is only in the last five years that cheap, accurate and almost universally compatible speech recognition systems have been widely available for accessing remote information sources.  Unfortunately, as is often the case, what improved hardware and software design can deliver often comes to a halt when we ask what the most effective and appropriate dialogue design is for a given purpose.  This is the problem we want to begin to address.

This paper will concentrate on some typical aspects of linguistic activity that can underlie the design of information retrieval dialogues.  These are dialogues where one agent (the source) has access to information in a specific domain and has to be able to interpret the input of a second agent (the client) so as to produce a relevant subset of its knowledge base to fulfil the information needs of the client.  Theoretically, the two agents could be themselves automated expert systems.  Examples would include market tracking software that is programmed to react to certain types of share movements, road navigation systems that compare knowledge of a vehicle’s movements against updates on traffic problems on local roads, and naval and aeronautical systems that optimise course choices in terms of changes in meteorological factors.  

Expert systems are relatively well-understood, because the underlying logic of the source information base and the executive client is the same.  Human clients are, ironically, less well understood in the sense that they do not naturally query the source in a completely transparent and logical way.  The same holds for human sources.  They interact with the other participant as a fellow interlocutor while trying to achieve the transactional goal of the information exchange and, far from holding up the information exchange, this seems to optimise the speed of getting the required information transferred.  
The approach of human participants is not so much reactive to explicit cues but is rather based on tacitly agreeing reciprocal roles in the encounter, on what the common task is, and on what the goals and the information status of the other participant are.  These goals are, therefore, as much interpersonal as to do with achieving the transaction of information transfer.  Sometimes the responses can be seen as coherent - in that they make sense in the task context - rather than cohesive -meaning that the sequence is signalled in dialogue terms.  We will return to this below.

As a result, it is important to start by looking at evidence based on human-human knowledge elicitation.  When we do this, we see that the outcome is very much attuned to the mutual understanding between client and source - often without subtasks being explicitly stated.  The specific dialogue type which we are concentrating on is where the source is an interface to an intelligent knowledge-based system and the client is an untrained human user with an interest in accessing one piece of specific kind of information in a fixed domain.  All of the data I draw on is derived from BT’s VODIS corpus, an extensive series of information request transcripts where a user telephones one of a variety of sources and attempts to elicit information to do with travel needs, including coach and train services, restaurants, sightseeing etc.

The most striking characteristic - obvious after even a cursory examination - is that there are two main intertwined activities going on.  From the start the two interactants assume congruent roles and automatically ascribe to each other motives derived from their own experience.  This runs parallel to the most high profile task of information transfer, and is maintained and checked on an ongoing basis.  Thus as well as transacting an information exchange, the interactants are also collaborating in generating a collaborative environment, mutually protecting and assigning what Goffman calls face.[6]  By intruding on the space of another person -for example by telephoning - this needs propitiatory rituals such as asking if the other could tell you something other than ordering them to tell you.  

All of this can be characterised in the relevant situational context in terms of field, mode  and tenor [7].  The field of the information request dialogue is defined by what the relevant information is and the processes that are used to elicit it..  The mode is a description of the channel of communications that apply - in this case non-face-to-face spoken dialogue.  The tenor encodes the role relationship between the participants in the activity.  We will address this last first.

2  Tenor and Transactional and Interactional Goals

Face has to do with the duty on each participant to recognise the other’s underlying role in terms of the transaction the dialogue is designed to fulfil.  It is then incumbent on each speaker to cooperate in recognising and trying to fulfil the other’s goals.  This applies not only to the long-term strategic goals of the whole transaction, but also the short-term tactical goals designed to facilitate each phase of the process of defining what the client wants and what the system can provide.  Each participant has a status in relation to the other.  The source has the status of access to information valuable to the client and the client has the status of customer, who ultimately pays the bill.  Both owe to each other the respect based on their mutual status and above the bare necessities of the transaction. Failure on either party’s part to know their place could result in the discourse being abruptly curtailed.  

In the following dialogue, for example, the transaction would be fulfilled by the response “2.17”, but what in fact happened was as follows

Railway Company.

Oh yes, could you tell me when the next train from Trimley to Felixstowe is?

Trimley to Felixstowe 

Yes.

What’s the time now?  Ten past one.  Oh dear, it’s not for an hour, I’m afraid.  2.17.

2.17.  Okay, thanks a lot.

‘Bye.

‘Bye.

Here the client uses a rather complicated form of words to avoid asking the question in blunt terms.  The source then takes on, unasked, the responsibility for the inconvenience of there not being an earlier train  Oh dear … I’m afraid.  This is very common in the data, and is classed as interactional since it is not central to the transaction, which is about finding out a train time.  There are of course some grey areas as for instance if the dialogue was a formal complaint.  In this case, the goal of the transaction is to address the grievance and so Sorry and I’m afraid could legitimately be regarded as transactional.

The corollary for automated systems is that we must be aware of such  expectations on behalf of the client, and at the very least, not run counter to them.  How far we should attempt to emulate expressions of solidarity such as the above on non-human interactants is probably a matter for further study.  

3  Dialogue Sequences

In addition to the importance of appreciating the tenor of a dialogue there are several important aspects of the structure of the usual transactional dialogue.  At the macrostructural level dialogues can be seen as consisting of, firstly, a boundary phase of two parts - opening and closing - , and, more importantly, the medial phase or body where the crucial information is elicited and provided.  In both boundary and medial phases the dual view of language in the construction of reality, and language in the negotiation of participant face can be seen.  Unlike a single person reading a timetable for their own information, where the process is purely transactional, as soon as another person is involved at least some language is required to oil the interpersonal wheels.  From a functional point of view the interactants' behaviour is highly constrained in terms of the overall goals of the interaction, as we have seen above, but it has not been widely appreciated that the interactants enter into a collaboration in attacking the problem posed.

The source and the client,often explicitly, reinterpret the problem to be solved as a mutual task not just in the business sense of trying to solve it, but also in the sense that they engage in mutually congruent evaluation of it.  It becomes a joint problem where the source apologises for its existence and the client apologises for having inflicted the problem on the source, as we saw in the previous section.

This collaborative principle extends to relatively low level aspects of the lexicogrammar. Grammatical sequences have tended to be seen as confined to the sentence but, because of the collaboration of the participants in the joint production of the dialogue, the role of sequences running over the grammatical boundaries of clauses sentences is crucial.  Questions, for example, are not sentences but demands for a completion which gives the equivalent of a sentence.  All questions have built-in incompleteness.  Polar questions have the positive-negative axis unspecified.  Constituent questions have a constituent lexically unfulfilled.  In the second part of the question-answer sequence which is characteristically produced by the other participant the unfulfilled constituent symbol such as What time would you like to be at Swindon by?i is replaced by a referential symbol such as Well, around 9 to 10.  The answer is characteristically ‘ungrammatical’ if taken in isolation, but not in combination. The phrase around 9 to 10 replaces What time.

Sensitivity to the importance of completing such user gambits appropriately is crucial to efficient dialogue design.  Other sequences which relate to the overall task scheme of the dialogue as a whole include as well as Question-Answer, Problem-Solution, General-Specific and Situation-Evaluation.  These key words are signals of Clause Relations - the building blocks of discourse in general and dialogues in particular.  Different grammatical configurations of the same ideational content are related to different types of contextual meaning.  The problem is recognising them, since the logic of clause relations is often based on the pragmatics of the task rather than how one word relates to the next.  The human user, once engaged on the task automatically commits to the joint project.

In transactional dialogues like these, a statement of a need - I want … or  I’m interested in finding out… etc - is treated as a formal request.  Also the source often asks questions of the client. such as in the following excerpt:

Could you please tell me the time of a train to Fairford.

Fairford? There’s no station there, I’m afraid.  You trying to get to the air show are you?

How far such interpersonal interchanges are worth building into automated interfaces is still a matter for study but some clarificatory initiatives will be necessary to tailor the transactional information to the client’s needs.  Certainly we need a better appreciation of the way people see interpersonal dialogues before we can have any confidence in being able to automate them successfully.

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