1. A method for validating data changes made to a database, wherein the changes are made in the context of a transaction, using a rules database storing a plurality of rules, the method comprising: initiating the transaction in response to a transaction start instruction; identifying a set of data entities affected by one or more data changes made in the context of the transaction, the identifying comprising: after initiating the transaction, receiving one or more instructions specifying data changes to be made in the context of the transaction; for each data change instruction, adding identifiers of one or more data entities changed responsive to the data change instruction to a validation list; and adding identifiers of one or more dependent data entities of the changed data entities to the validation list; in response to an instruction to commit the transaction, validating data entities in the set of affected data entities using rules from the rules database, the validating comprising performing validation based on the data entities in the validation list; and committing the transaction in dependence on the outcome of the validation.