Comet: An Application of Model-Based Reasoning to Accounting Systems

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An important problem faced by auditors is gauging how much reliance can be placed on the accounting systems that process millions of transactions to produce the numbers summarized in a company’s financial statements. Accounting systems contain internal controls, procedures designed to detect and correct errors and irregularities that may occur in the processing of transactions. In a complex accounting system, it can be an extremely difficult task for the auditor to anticipate the possible errors that can occur and to evaluate the effectiveness of the controls at detecting them. An accurate analysis must take into account the unique features of each company’s business processes. To cope with this complexity and variability, the Comet system applies a model-based reasoning approach to the analysis of accounting systems and their controls. An auditor uses Comet to create a hierarchical flowchart model that describes the intended processing of business transactions by an accounting system and the operation of its controls. Comet uses the constructed model to automatically analyze the effectiveness of the controls in detecting potential errors. Price Waterhouse auditors have used Comet on a variety of real audits in several countries around the world.