Wednesday, 30 December 2015

Providing assurance of machine decision making

All Models Are Wrong But Some Are Useful” -George Box

The aim of Human-Machine Teams (HMT) is to make rapid decisions under changing situations characterised by uncertainty. The aim of much modern automation is to enable machines to make such decisions for use by people or other machines. The process of converting incomplete, uncertain, conflicting, context-sensitive data to an outcome or decision needs to be effective, efficient, and to provide some freedom from risk. It also may need to reflect human values, legislation, social justice etc. How can the designer or operator of such an automated system provide assurance of the quality of decision making (potentially to customers, users, regulators, society at large)? 'Transparency' is part of the answer, but the practical meaning of transparency has still to be worked out.

The philosopher Jurgen Habermas has proposed that action can be considered from a number of viewpoints. To simplify the description given in McCarthy (1984), purposive-rational action comprises instrumental action and strategic action. Strategic action is part-technical, part-social and refers to the decision-making procedure, and is a the decision theory level e.g. the choice between maximin, maximax criteria etc., and needs supplementing by values and maxims. It may be that Value Sensitive Design forms a useful supplement to Human-Centred Design to address values.

The Myth of Rationality

"Like the magician who consults a chicken’s entrails, many organizational decision makers insist that the facts and figures be examined before a policy decision is made, even though the statistics provide unreliable guides as to what is likely to happen in the future. And, as with the magician, they or their magic are not discredited when events prove them wrong. (…) It is for this reason that anthropologists often refer to rationality as the myth of modern society, for, like primitive myth, it provides us with a comprehensive frame of reference, or structure of belief, through which we can negotiate day-to-day experience and make it intelligible."
Gareth Morgan

The Myth of Rationality is discussed e.g.  here.  The limits of rationality (or perhaps its irrelevance) in military situations  should be obvious. If you need a refresher, then try Star Trek 'The Galileo Seven'. The myth of the rational manager is discussed here. This is not to say that vigilant decision making is a bad thing - quite the opposite. As Lee Frank points out, rationality is not the same as being able to rationalise.

The need for explanation / transparency

The need for transparency and/or observability is discussed in a previous post here. There is an interaction between meeting this need and the approach to decision making. AFAIK the types of Machine Learning (ML) currently popular with the majors cannot produce a rationalisation/explanation for decisions/outcomes, which would seem a serious shortcoming for applications such as healthcare. If I am a customer, how can I gain assurance that a system will give the various users the explanations they need?

Approach to decision making

It is the mark of an educated man to look for precision in each class of things just so far as the nature of the subject admits; it is evidently equally foolish to accept probable reasoning from a mathematician and to demand from a rhetorician scientific proofs.” Aristotle
At some point, someone has to decide how the machine is to convert data to outcomes (what might have been called an Inference Engine at one point). There is a wide range of choices; the numeric/symbolic split, algorithms, heuristics, statistics, ML, neural nets, rule induction. In some cases, the form of decision making is inherent in the tool used e.g. constraint-based planning tool, forward-chaining production system, truth maintenance system etc. There are choices to be made in search (depth vs. breadth) and in types of logic or reasoning to be used. There were attempts before the AI winter to match problem type to implementation but IMHO they didn't finish the job, and worked-up methodologies such as CommonKADS would be a hard sell now. So, what guidance is available to system designers, and what forms of assurance can be offered to customers at design time? Genuine question.

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