A structural model of discourse for natural language interaction developed for the LINLIN-system is evaluated using the Wizard-of-Oz method. 21 dialogues were collected using five different background systems, making it possible to vary the type and number of tasks possible to perform by the users. The results indicate that the structural complexity of the discourse in man-machine dialogues is simpler than most human dialogues, at least for information retrieval and some types of ordering systems, suggesting that computationally simpler discourse models can be used in these domains.

We describe an empirically based approach to the computational management of dialogues. It is based on an explicit theoretically motivated position regarding the status of computational models, where it is claimed that computational models of discourse can only be about computers' processing of language. The dialogue model is based on an extensive analysis of collected dialogues from various application domains. Issues concerning computational tractability has also been decisive for its development. It is concluded that a simple dialogue grammar based model is sufficient for the management of dialogues with natural language interfaces. W e also describe the grammar used by the dialogue manager for a Natural Language interface for a database system.

Distributed cognition is a perspective that primarily has been applied to complex socio-technical systems such as flight decks of commercial airliners, or operating rooms where professionals perform cognitive tasks in environments specifically designed for this. For some scholars distributed cognition is exactly this kind of specialized cognitive system. On the other hand it has been claimed by some workers in the field that distributed cognition is not a kind of cognition but a perspective on all cognition. We have therefore studied an environment very different from the systems previously studied, namely single people’s homes. We find that there are many similarities between the home and the specialized socio-technical environments. To us this suggests that the specially designed complex environments can be seen as specialized cases of the general principles of distributed cognition which are not reflections of “particular work practices” but of general features of human cognition.

We present the results of a study of spatial cognition and its relationship to hypermedia navigation. The results show that a distinction can be made between two kinds of spatial cognition. One that concerns the concomitant acting in the physical world, and on that is a pure internal mental activity. This conclusion is supported by two kinds of data. First, a factor analysis of the subtests used in this study groups them into these two categories, and second, it is shown that only the internal one of these factors is related to the subjects performance in using a hypertext-based on-line help system. In the fmal section we point to the theoretical connections between this work and work in areas of situated cognition and on different kinds of mental representations, and discuss various possibilities that the results from this study suggest for the development of interface tools that will help users with low spatial abilities to use hypermedia systems.