1. A method for testing at least one data item in a transaction order against at least one business logic rule, the method comprising the steps of: creating a repository of executable rules, each executable rule adapted to encode a business logic rule; listing a subset of executable rules to be used in checking said transaction order, at least one listed executable rule being adapted to test said at least one data item against at least one business logic rule; locating the listed subset of executable rules in the repository; causing said at least one executable rule of the subset to test said at least one data item against said at least one business logic rule; and indicating whether said at least one data item conforms to said at least one business logic rule.