Section 17.4.1:
Providing the transaction attributes for an enterprise bean is an optional requirement for the Application Assembler, because, for a given enterprise bean, the Application Assembler must either specify a value of the transaction attribute for all the methods for which a transaction attribute must be specified, or the Assembler must specify none. If the transaction attributes are not specified for the methods of an enterprise bean, the Deployer will have to specify them.
Transaction attributes have to be specified at the latest just before deploying the beans otherwise the container won't deploy the beans...