Construct Algebra: Analytical Dialog Management

In this paper we describe a systematic approach for creating a dialog management system based on a Construct Algebra, a collection of relations and operations on a task representation. These relations and operations are analytical components for building higher level abstractions called dialog motivators. The dialog manager, consisting of a collection of dialog motivators, is entirely built using the Construct Algebra. 1 I N T R O D U C T I O N The dialog manager described in this paper implements a novel approach to the problem of dialog management. There are three major contributions: the task knowledge representation, a Construct Algebra and a collection of dialog motivators. The task knowledge representation exploits object-oriented paradigms. The dialog motivators provide the dialog manager with the dialog strategies that govern its behavior. The Construct Algebra provides the building blocks needed to create new dialog motivators and analyze them. The first main component of this dialog manager is the task knowledge representation. The task knowledge is encoded in objects. These objects form an inheritance hierarchy that defines the relationships that exists among these objects. The dialog manager exploits this inheritance hierarchy in determining what queries to pose to the user. No explicit states and transitions need to be defined using this framework (Bennacef et al., 1996; Meng and et. al., 1996; Sadek et al., 1996). A change to the dialog does not require a change to the dialog manager, but more simply, a change to the inheritance hierarchy. The second main component of this dialog manager is the collection of dialog motivators. The dialog motivators determine what actions need to be taken (e.g. ask a confirmation question). The dialog motivators are founded on a theoretical framework called a Construct Algebra. The Construct Algebra allows a designer to add new motivators in a principled way. Creating a new application requires defining the inheritance hierarchy and perhaps additional dialog motivators not encompassed in the existing collection. This dialog manager has been used for two applications. The first is a spoken dialog system that enables a user to respond to the open-ended prompt How may I help you? (HMIHY) (Gorin et al., 1997). The system recognizes the words the customer has said (Riccardi and Bangalore, 1998) and extracts the meaning of these words (Wright et al., 1998) to determine what service they want, conducting a dialog (Abella and Gorin, 1997; Abella et al., 1996) to effectively engage the customer in a conversation that will result in providing the service they requested. The second application is to Voice Post Query (VPQ) (Buntschuh et al., 1998) which provides spoken access to the information in large personnel database (> 120,000 entries). A user can ask for employee information such as phone number, fax number, work location, or ask to call an employee. These applications are signifi-