Rules play a very important role in transaction objects, as they allow you to program their behavior (for example: assigning default values, defining controls over the data, etc.).
They are written in a declarative way, which means the order in which they are written is not necessarily the order in which they will be executed.
They may involve the attributes included in the transaction's structure (all transaction rules can involve attributes of the base tables associated to the transaction, and most rules
can also involve attributes of the extended tables of such base tables -but they must be included in the transaction's structure-) as well as variables defined within the object, constants and functions.
They are only valid within the transaction in which they are defined, that is to say, they are local.
Some valid rules for transactions are: