Goal-Directed Diagnosis-Diagnostic Reasoning in Exploratory-Corrective Domains

In many diagnosis-and-repair domains, diagnostic reasoning cannot be abstracted from repair actions, nor from actions necessary to obtain diagnostic information. In general, in exploratory-corrective domains an agent has to interleave exploratory activity with activity aimed at achieving its goals. In TraumAID 2.0, a consultation system for multiple trauma management, we implement a reasoning framework for such domains which integrates diagnostic reasoning with planning and action. This paper presents Goal-Directed Diagnosis (GDD), a formalization of TraumAID 2.0’s diagnostic reasoning. Taking the view that a diagnosis is only worthwhile to the extent that it can affect repair decisions, GDD uses goals to focus on such. Goals are also useful as a means of communicating with its accompanying planner. 1 Background and Motivation In many domains, it is common to distinguish reasoning and activity concerned with what problems need be addressed from that reasoning concerned with how to address those problems. As such, Artificial Intelligence (AI) subsumes as separate sub-disciplines diagnosis research, seeking the source (or sources) of a system’s faulty behavior, and planning research, concerned with the construction of action plans to achieve certain goals. Based on that dichotomy, most formalizations of diagnosis aim at a diagnosis object as a solution. In some domains, however, this may be inadequate. In trauma management, for one, therapy is the ultimate objective and diagnosis is the “price” that one has to pay in order to achieve that objective. In such domains, we argue, diagnosis should only persist so long as it can affect those decisions for which it was carried out in the first place, namely repair decisions. We call this the Goal-Directed Diagnosis (GDD) principle. The GDD principle suggests that diagnostic and therapeutic decisions be considered together. Furthermore, in many diagnosis-and-repair domains multiple diagnostic and therapeutic needs require, and compete for, the agent’s activity. In This work was supported in part by a graduate fellowship, ARO Grant DAAL03-89-C0031PRI, and by a National Library of Medicine grant 1RO LM051217-01. [Rymon, 93], we propose an Exploratory-Corrective Management (ECM) architecture (Figure 1) employing a basic cycle of diagnostic reasoning, planning and action. Reasoner Planner goals Physician evidence plan characterization TraumAID 2.0 Figure 1: The ECM Architecture In this architecture, diagnostic and therapeutic goals are uniformly posted to the planner, who is charged with addressing them as a combination. For exploratory-corrective domains such as trauma management, the ECM architecture satisfies the following desiderata: 1. it allows interleaving diagnosis and repair. 2. it positions the diagnostic reasoner to (a) set diagnostic and therapeutic goals; (b) use incoming evidence to monitor actions and other events, reason about changes in knowledge or state, and adapt goals; 3. it positions the planner to mediate between concurrent diagnostic and therapeutic needs. TraumAID is a consultation system for the diagnosis and treatment of multiple trauma (for an overview see [Webber et al., 92]). TraumAID 2.0, its new ECM-based version, has recently been judged by a panel of trauma surgeons as significantly more acceptable than actual care.1 . This paper formalizes TraumAID 2.0’s goal-directed diagnostic reasoning. It is structured as follows: Section 2 reviews related work; Section 3 formalizes GDD; and Section 4 discusses its use within the ECM framework to implement a variety of diagnosis-and-repair strategies. Three trauma surgeons were asked to blindly compare the actual care in 97 trauma cases to the management that would have been proposed by TraumAID 2.0. The judges indicated a significant preference for TraumAID 2.0 plans over actual plans by a ratio of 64 to 17 with 16 ties (p <0.001 by binomial test). For more details see [Rymon, 93].