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Decision Support Systems

Computers have been used to support human decision-making for several decades, and increasingly, formal argumentation models are being used in their design. However, their use raises a number of conceptual and social-ethical questions that have yet to be fully addressed. We explore some questions raised by two current proposals for computer-mediated argumentation and decision-making, in particular the assessment of substantive quality, inclusiveness, and noncoerciveness, as these bear on legitimate policy decisions. Human reliance on computer technology is by now a well-established cultural fact.

Indeed, we now rely on computers even for certain forms of decision-making: so-called “knowledge-based expert systems,” or “decision support systems,” have been developed over the last thirty or so years to support, or sometimes even replace human decision-making (Alty and Coombs 1984; Buchanan and Shortliffe 1984). As the name suggests, expert systems attempt to automate (by means of a knowledge base and inference mechanisms) the knowledge and reasoning skills of experts in a given domain, such as medical diagnosis, marketing decisions, and so on.

In this essay we are concerned with recent attempts to develop decision-support systems for processes of public policy argumentation. Like earlier expert systems, these argumentation-support systems incorporate both knowledge bases and inference mechanisms. Unlike the earlier systems, however, they place greater emphasis on the processes used for reasoning and inference than on the database of knowledge from which conclusions are drawn; thus we might designate them as “argumentation systems” in contrast to the earlier “knowledge systems.

Dialectical approaches in particular have drawn attention in this developing area of Artificial Intelligence research. Indeed, some commentators have recommended the employment of such systems, via the Internet, to enable democratic participation in public policy decision-making processes (e. g. Ess 1996). The kind of argumentation systems we examine here are noteworthy for their attempt to draw explicitly upon dialectical theories of argumentation as a framework for processes of public deliberation involving multiple parties and interests.

The use of argumentation systems to assist public deliberation raises a number of conceptual and social-ethical questions that have yet to be fully addressed. On the one hand, argumentation systems provide a deliberative forum whose results can advise and, one hopes, improve the quality of decisions. If appropriately designed, such systems should be able to assist debate by tracking the various claims and arguments, by searching databases for relevant information, and by continually updating and assessing the overall state of the debate.

They thereby help participants argue in a dialectically responsible manner, while offering them ample scope for modifying aspects of the system, such as the stock of inference rules and proof standards. On the other hand, the highly qualitative and publicly controverted character of public policy argumentation pose serious questions about what would constitute an “appropriate design. ” In this paper we aim to clarify the criteria for an appropriately designed argumentation system.

To focus and concretize the discussion, we start by describing, in Section 2, two current proposals for computer-mediated argumentation and decision-making, the Zeno system of Gordon and Karacapilidis and their colleagues at the German National Research Centre for Information Technology and the Risk Agora of McBurney and Parsons. In Section 3 we elaborate the basic evaluative dimensions appropriate for the deliberative contexts in which such systems are to be used. In the subsequent sections we indicate how one might apply these deliberative criteria for assessing the two argumentation systems.

As we shall see, the critical assessment of argumentation-support systems must draw upon an understanding of the discursive bases of responsible public legitimation and must acknowledge inherent limits on what formal design features can achieve for legitimation. We begin by describing the two argumentation systems. The first is the Zeno system of the German National Research Centre for Information Technology (GMD) (Gordon and Karacapilidis 1997, Gordon et al. 1997, Karacapilidis et al. 1997).

Zeno was developed to support decision-making in urban planning, as part of a larger European Community-funded project to develop innovative information systems infrastructure for public collaborative environmental planning. In these domains, there are multiple interested parties, with diverse professional or private backgrounds, interests, preferences and viewpoints, and they are often geographically dispersed. Because the application domain of Zeno involves urban planning decisions, the system has to integrate information which is spatially indexed with information which is not.

And because the users may be diverse and geographically distributed, the system requires intuitive and easy-to-use interfaces, provided, preferably, across an internet platform. Neither of these elements of software design was technically straightforward, but these issues will not concern us here. Our focus is on the argumentation and decision support elements of Zeno. The developers of Zeno define their system as “a mediation system”: “a kind of computer-based discussion forum with particular support for argumentation.

In addition to the generic functions for viewing, browsing and responding to messages, a mediation system uses a formal model of argumentation to facilitate retrieval, to show and manage dependencies between arguments, to provide heuristic information focusing the discussion on solutions which appear most promising, and to assist human mediators in providing advice about the rights and obligations of the participants in formally regulated decision making procedures. ” (Gordon and Karacapilidis 1997, p. ).

The argumentation model used by Zeno is a formal version of the informal Issue-Based Information System (IBIS) model of Rittel and Webber (1973), modified for the urban-planning domain. The IBIS model identifies several atomic elements of a discourse: Issues, the topic about which a discussion is conducted; Positions, which express some statement relevant to an issue; and Arguments, which present statements in favour or against particular Positions.

Thus (using an example from Karacapilidis et al. 97), an Issue may be: “Which site should the airport be located? “; Positions may then be statements designating different alternative sites, or groups of possible sites; and Arguments may be positive and/or negative attributes about these site alternatives and statements, such as: “Has easy access” or “Is private land. ” Each element of this model can be attached to each other element at any time, so that, for example, a new issue can be raised at any point in a discussion, thus creating a subsidiary discussion on the new issue.

The IBIS model is well-suited for the display of a discussion as a hierarchical graph; the implementation of hypertext links enables a user to move easily around this graph from one thread of a discussion to another, or to access background data, supporting documents or contextual information, etc, associated with any element of the discussion. Among the objectives of the Zeno project is to enable snapshots of a debate: “One important goal is to provide easy access to the current state of the planning process, at any time. ” (Gordon et al. 1997, Section 2).

In order to provide for these, the designers of Zeno modified the IBIS model to permit the expression of preferences. Positions have the form of logical propositions but they do not have a context-independent truth status. Their meaning is defined by their role in a particular thread of discussion. Preferences are defined as particular types of positions with an internal structure of comparison of two (non-preference) positions. For example, two planning options for siting an airport, such as “public site” and “easy access” might enter into a preference that considers easy access as “more important than” a public site.

This preference then constitutes a qualitative constraint, which may or may not be supported by further arguments (i. e. , positions), and which may or may not be consistent with other constraints. These preferences and constraints, being positions, may themselves be the subject of discussion, via the articulation of arguments and the raising of further issues. Zeno provides users with an overview of the argumentative status of positions, preferences, and constraints. By considering to extent to which each position satisfies the articulated constraints, Zeno permits positions to be labeled as acceptable or not at any time in a discussion.

These position-labels can then be aggregated in various ways to assign labels to Issues, and Zeno does this to indicate the extent to which their current argument support meets defined standards of proof. The Zeno developers argue that no set of proof-standards is applicable across all application domains, and so they adopted a set of five labels from the field of jurisprudence, namely: (1) Scintilla of Evidence; (2) Preponderance of Evidence; (3) No Better Alternative; (4) Best Choice; and (5) Beyond a Reasonable Doubt (Gordon and Karacapilidis 1997).

Each label is provided with a formal definition in terms of the presence or absence of positions and arguments (although these definitions are not claimed to be instantiations of the legal definitions of these terms). With this argumentation structure, it is then straightforward for the system to present to a user the current status of a discussion and to show this as it changes.

The designers of Zeno identify the generic speech acts involved in contributing to a discussion, for example, “Raise an issue”, “Assert a position”, “State a preference”, etc (Gordon and Karacapilidis 1997). However, they do not, in the work published to date, articulate a definitive list of such speech acts or the rules that govern their use. By contrast, our second example of an argumentation system, the Risk Agora of McBurney and Parsons (2000,2001b,2001c) is fully specified in this manner, and we now discuss this system.

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