The Rational Actor Approach is centered on the principal assumption that if human decision makers are provided with complete information on the possible results and options in the choices that they have to make, they would choose the optimal alternative, or the option with the maximum possibility of turning out to be the outcome that is most wanted or desired. This being true, the goal of the DSS is to enable the decision maker to select construction materials as per their sustainability so that the vast majority of the materials selected for construction are sustainable materials.
The rational actor model has three phases (Simon, 1983): Phase 1: Determining all choices that are possible. Phase 2: Analyzing every choice for the consequences that it they may lead to. Phase 3: Finally choosing an alternative that is rated as the best based on considerations of utility and the most probable consequence or output.. In the DSS, the Rational Actor Model can be further fine tuned by the adoption of a few modifications.
First, the material alternatives that are obviously not suitable for the project element could be pruned off the database based on classification of materials according to some given standards. The software will therefore prune materials such as ceramic tiles when considering the construction of a foundation footing column. This eliminates the possibility of users ignoring feasible but unfamiliar materials. A second modification could be the introduction of user weightings for each sustainability attribute.
The weightings are a way of personalizing or customizing the system. Input of the weightings accord the methodology adopted in the system higher acceptability for the user who provides the weightings. The weightings also enable customization of the sustainability of the final design product. (Pearce, et. al. , 2001). The ordered stages of the methodology adopted with modifications can now be defined for the Decision Support System. In its first step, the methodology generates the alternatives that would be available for making the selection.
This is a comprehensive set of alternatives that could include all the materials available in the market. In its second stage, the clearly infeasible alternatives are pruned from the list of available alternatives through the application of some technical performance thresholds or other heuristics. This would result in a set of alternations that are all feasible for the application under consideration. The crucial third step consists of the Decision Support System ranking the alternatives based on the sustainability and utility of the material for the use that it is intended for.
At this juncture, the decision maker feeds in his weights for each attribute of sustainability as per the priority that particular attribute holds for the decision maker. Manufacturer information and other sources determine the values for the sustainability attributes of each material, and a normalized value is worked out for each value of the attributes. The weights and normalized values for the sustainability attributes of each material are then multiplied and added together to produce the index of subjective utility for that material.
A ranking of the alternatives is developed by sorting their utility values. The Decision Support System then outputs the alternative with the highest utility value to the user. The decision maker is at liberty to choose the highest ranked alternative for the particular application or any other alternative as he or she may deem suitable from the point of view of cognitive abilities and professional experience. The DSS then moves on to take up other design elements for consideration.