Ontologies and ontology-based information systems are becoming more commonplace in knowledge management. For engineering applications such as product design, ontologies can be utilised for knowledge capture/reuse and frameworks that allow for the integration and collaboration of a wide variety of tools and methods as well as participants in design (marketing/sales, engineers, customers, suppliers, distributors, manufacturing, etc.) who may be distributed globally across time, location, and culture. With this growth in the use of ontologies, it is critical to recognise and address errors that may occur in their representation, maintenance and utilisation. Passing undetected and unresolved errors downstream can cause error avalanche and could diminish the acceptance, further development and promise of significant impact that ontologies hold for product design, manufacturing, or any knowledge management environment within an organisation. This paper categorises errors and their causal factors, summarises possible solutions in ontology and ontology-based utilisation, and puts forward an ontology-based Root Cause Analysis (RCA) method to help find the root cause of errors. Error identification and collection methods are described first, followed by an error taxonomy with associated causal factors. Finally, an error ontology and associated SWRL (Semantic Web Rule Language) rules are built to facilitate the error taxonomy, the root cause analysis and solution analysis for these errors. Ultimately, this work should reduce errors in the development, maintenance and utilisation of ontologies and facilitate further development and use of ontologies in knowledge management.

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Operations researchers, industrial engineers, and simulation analysts have applied their knowledge and skills to the health care system for a long time. This complex system needs their help today more than ever. The ever-growing need to understand and improve system performance challenges researchers to apply all the tools at their disposal. One of these tools that is getting increased attention is system thinking, with its application partner system dynamics. This paper presents a glimpse into the system thinking world as it is currently applied in the health care arena, and provides some thoughts on new directions for application. While there are other very useful tools, such as optimization and discrete-event simulation, that are effectively used for health care application, they should not always be the tools of choice, and suggestions are made for when system dynamics may be more appropriate for a particular application.