Exposure assessment is an expert task, requiring an experienced occupational chemist, as many of the chemical and physical properties of a new substance are not known to the assessor a priori.
For the system to be deployed, it must incorporate best practice knowledge engineering techniques and, as there are safety-related considerations and AIAI and the HSE are committed to quality, the work had to be carried out in accordance with ISO9001 standards.
The system guides the user by offering a menu of appropriate choices whenever it needs information. When numerical values must be provided, e.g. vapour pressure, sanity checks are carried out.
The user can always back-track and change the answer to an earlier question.
A full explanation of the conclusion is always given, and an explanation of why a particular question is being asked is always available. Each guidance session is logged.
The Knowledge-based approach allowed the system to be implemented as three separate modules: inference engine, knowledge base, and user interface. Initially required to run under MS-DOS on a PC AT equivalent with 640K of RAM, a second release to run under Windows 3.1 reused the inference engine and knowledge base, requiring only a revised user interface. Enhancements made to the inference engine and the knowledge base were immediately available to both environments.
The system has been widely distributed for use by authorities throughout Europe.