System and method for consistency constraint management in database middleware

摘要

A system and method for constraint management in a database middleware system that responds to queries for data from requesting user applications by accessing diverse data sources. A constraint manager receives notifications of updates from sources that support notification, and the constraint manager monitors other sources that support monitoring, to undertake constraint management. Repairs of inconsistencies are made when possible, and when repairs are not possible, the inconsistencies are nulled out if the inconsistencies are totally useless to the requesting user application. In contrast, if the requesting application has some use for otherwise inconsistent, unrepairable data, the data is sent to the application along with an alert of the inconsistencies. Also, for those sources that do not support either notification or monitoring, the constraint manager executes just-in-time checking, i.e., when a query is received, the constraint manager checks data that is to be accessed pursuant to the query, and if inconsistencies are found, the inconsistencies are virtually repaired, i.e., data received from the source is repaired at the constraint manager. The query is then executed against the repaired data.