Customer Stories

The Safety Engineering Unit
Studies Human Reliability
with the Ovenman, C++ and Amzi!

The ovenman's principle task is to change uncooked cakes into correctly cooked cakes. A correctly cooked cake is a cake which is not overcooked or undercooked. To achieve this task the ovenman must prepare a plan of oven settings that will cause the oven to turn out the current batch of cakes correctly cooked. A plan is necessary because the available oven settings cannot usually be made to correspond exactly to the associated cooking time and cooking temperature of the cakes. An added complication is provided by the variability of the cake mixtures and the ovenman's 'fuzzy' knowledge of the cooking times and temperatures of the cakes. There are no written instructions detailing how a type of cake should be cooked. The ovenman relies purely on his expert knowledge to judge the appropriate oven settings and the condition of the cakes when viewed through the oven inspection ports.

The ovenman is not supposed to be a robot who does everything perfectly all of the time. He is supposed to be more human and as such he is expected to make mistakes. HRA techniques used in this study are designed to quantify the likelihood of a mistake being made. In theory then, all that has to be done to make a 'human' out of the ovenman is to apply an HRA technique to the model to predict the errors he will make. In effect the HRA technique dictates the behaviour (or divergence from optimum performance) of the ovenman.

The ovenroom and its contents and the main driver module are programmed in C++ for its object orientedness and diversability. The ovenman is programmed using Amzi! Prolog and controls the ovenman's diagnosis of the situation, selection of appropriate action i.e. what to do next, and execution of the action. Prolog was chosen for its built-in inference engine and Amzi! because of the ease with which their Prolog can be integrated with C++ and Windows.

Allan Boyd
Safety Engineering Unit
University of Aberdeen