Ontology-Supported Scaffolding for System Safety Analysis

System Safety Analysis is a valuable task used when trying to ensure that any thing that can be represented with the systems-model does not behave in some manner that is undesirable to the stakeholders in that system. It's a creative task, with no known correct solution, with limited tool support. This thesis investigates the possibility of providing support to analysts undertaking this task through the use of ontology and pedagogy in an artificially intelligent tool. An ontology to capture the system-model as understood by System-Theoretic Accident Model and Processes (STAMP) was authored, building on an existing set-theoretic representation. This required the authoring of underlying ontology-modules, including one for Control Systems and one to capture sufficient information for use with Situation Calculus. Together these capture information to be used in reasoning about system behaviour. During System Safety Analysis a user extends this ontology to model their system, and the intelligent support tool interprets it to offer its advice. The intelligent support tool uses Contingent Scaffolding to tailor its support to the user, this pedagogical strategy was chosen as it's been shown to enable the learner to produce a better quality product than they would be capable of alone. Contingent Scaffolding depends upon knowledge of past behaviour of the learner so that interventions can be pitched at the correct level for the learner. Typically ontology authoring tools use a synchronic view of the ontology, and so don't capture the required history. This tool uses Situation Calculus to capture a diachronic view of the ontology such that the history of authorship can be reasoned with to apply the Contingent Scaffolding framework defined herein. To evaluate the practicability of this approach the ontology and scaffolding were implemented in software. This surfaced an issue with the inability to inverse dependencies in Prolog, which was important to make the tools reuseable and shareable. These were overcome by Protocols provided in Logtalk. The code was then applied to other domains, such as robotics planning by a third-party, demonstrating generalisability of the intelligent support tool. A user study was conducted to evaluate the effectiveness of the intelligent support tool, in which novices undertook a System Safety Analysis. The tool was able to effectively provide support where definitions were missed and additional patterns of behaviour were identified that are indicitive of the user needing support. The thesis makes a number of contributions including: a systems ontology with a focus on capturing hypothetical and realised behaviour, a formal definition of a contingent scaffolding framework that can be used with ill-defined tasks, and the use of dependency inversion in Prolog to enable sharing of libraries. The primary contribution is in the use of a diachronic view of ontology authoring to provide support, which has been successfully exploited and has scope for providing a platform for many more applications.