Dialogue systems(DSs) which guide the users to access web services and information can improve the usability and accessibility of the web content. Although voice interfaces providing access to the web already exist, most of them only support simple dialogues.
One of the most relevant works in the area of commercial voice systems is the definition of the VoiceXML language, the standard widely adopted to provide telephone access to the web content. The VoiceXML language is appropriate to define simple dialogues, which ask the users to give the specific information the service needs. However, VoiceXML systems only support very limited user initiative (the user can only choose the order in which the information asked by the system is given) and they do not support complex dialogue phenomena, such as clarification. Besides, in VoiceXML systems all possible sequences of interaction have to be defined for each service. Furthermore, in those systems only the voice mode is supported.
On the other hand, there are research DSs which use domain and dialogue management models and have reusable components of discourse management and language (such as ,, ). Several of those complex DSs achieve a friendly communication. However, the cost of developing those DSs from scratch is high and their adaptation to support telephonic access to different types of web services requires some efforts.
In this paper, we are concerned with the integration of a dialogue manager (DM) component into a multilingual DS (), based on VoiceXML, which supports access to online public administration services. The incorporation of the generic DM component, which supports rich communication, improves the friendliness and portability of the DS. Additionally, a component for text processing has also been incorporated into the DS to support text mode and to enhance improve the voice recognition module.
In this section we describe how language and dialogue management technologies have been integrated in the DS we developed to access the web content. The architecture of the DS is shown in Figure 1.
The DM component controls the dialogue flow. In order to achieve a friendly communication this component uses an explicit dialogue model which defines general dialogue mechanisms, such as feedback strategies. The DM follows the issue-based approach explained in , which describes dialogues in terms of issues being raised and resolved. In our system, these issues basically consist of the service tasks and their parameters.
The DM uses communication plans to determine which is the issue raised by the user and how to solve it. The DM uses these plans to recognize when the user asks for a specific service task (from a set of possible tasks) and when he provides the information necessary to perform a service task, even when no question about it has yet been raised.
Let us consider the following example of dialogue:
S1:Welcome to the automatic platform of Barcelona. Choose one service available: large objects collection service or cultural agenda
U1:Iím looking for movies in the Filmoteca
S2: Ok, you are interested in the title of the event. Ok, the event type is cinema. The place is Filmoteca.
*** database consultation
The system asks the user to choose between one of the two services supported: the transactional service for large objects collection and the informational service about cultural events. The user does not answer the question, instead, he asks for information about movies. The DM gets the interpretation of the userís intervention ([ask, [event-type, cinema],[location, filmoteca]]) and finds that this information is the answer to questions in the communication plan for the cultural agenda.
Communication plans can be decomposed into actions and subplans. Possible plan actions are ask, answer plus the system actions to access the web services. To reduce complexity in dialogue management the plans are generated statically, when a new service is incorporated. To facilitate the generation of plans we have defined templates which describe general plans for two different types of web services: transactional and informational.
We have followed the information state-based theory to implement the DM component. This theory is based on a rich representation of dialogue context (the information state). In our DM, the information state consists of two parts:
There is a set of rules which govern the way the information state is updated and the next system dialogue actions.
In order to support a friendlier communication the speech recognition component (from the Loquendo VoiceXML platform) has been adapted to recognize a broader range of usersí interventions. The automatic speech recognition uses grammars (in the standard SRGS formalism) to model possible userís input. Recognition grammars limit the userís interventions which can be understood to what the grammars themselves allow. In the previous prototype of the DS the voice grammars modelled the possible userís answers to the last system message. In order to cope with other possible userís interventions, these voice grammars have been extended.
We have incorporated a natural language parser and processor (NLPP) to enhance the capabilities of the voice recognition module. The recognized input (transformed in text) is passed to the NLPP which performs a deep syntactic and semantic analysis. The NLPP uses domain independent linguistic resources as well as domain-restricted lexicons and ontologies.
When a new web service is incorporated into the system, the appropriate systemís prompts are generated automatically in the four languages supported by the system:English, Spanish, Catalan and Italian. In order to obtain the most appropriate systemís prompts for a specific service, the generator component uses a syntactic-semantic taxonomy which relates the specific service tasks and parameters to the linguistic structures needed for their expression.
We have distinguished two types of users: novices and experts (they have used the system before). Systemís prompts for novice users guide them to give all the data the service needs. Systemís messages for expert users are more open. For example, in the dialogue described aboved, the user has been considered a novice. If the user is considered an expert, the first systemís message is ďWelcome to the automatic platform of Barcelona. May I help you?Ē.
The evaluation of the performance of the DM component using only the text mode has proven that simple dialogues in which the system asks the user for specific information are appropriate for transactional services but more flexible dialogues are required for informational services (when user searches for different information). The evaluation of the performance of the definitive prototype of the system is planned for the following months. Future work will also include the adaptation of the DS to other types of web information.
This work has been supported partially by the EU IST FP6 project HOPS (IST-2002-507967, http://www.hops-fp6.org/).
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