The invention introduces a method and system to automatically derive the relationships between query subjects and query items within query subjects so that problems such as those that result in double courting of information are avoided. It provides for creating a report by first defining a model based on an existing database comprising two or more query subjects, each query subject comprising at least one fact query item and one primary key, then generating a hierarchy of sets and subsets of key query items within the model. Next a further fact is introduced into one of the query subjects. The expression is decomposed into sub-queries to prevent double counting of data in ambiguously defined situations. This is achieved using the introduced fact to determine that such decomposition is required. Finally, the data is accessed using the sub-queries, and a report is produced.