A knowledge base and methods for use in connection with a policy compliance monitoring system operative to determine exceptions to policies expressed by computer-executable policy statements. The system allows establishment, codification, and maintenance of enterprise policies, monitors electronic transactions of the enterprise from various and possibly heterogeneous data sources, detects exceptions to established policies, reports exceptions to authorized users such as managers and auditors, and/or provides a case management system for tracking exceptions and their underlying transactions. The knowledge base comprises extractor files that are utilized for extracting information from data sources for utilization in policy compliance monitoring, a mapper for normalizing data from the data sources against a system ontology and storing normalized data in a monitoring database, and computer-executable compliance policy statements used by a transaction analysis engine. The policy statements represent predetermined policies of the enterprise that apply to data stored in the monitoring database.