The original STAR Transport Guidelines required that the transports provide the ability to deliver messages reliably. However, theory did not always lead to reality. The state of the WS-ReliableMessaging frameworks at the time did not lead to interoperable or easy to deploy implementations. STAR does not specify when or how to use reliable messaging, that is up to the trading partners. The STAR Level 2 rules on WS-Reliable Messaging only state what needs to be supported to help provide the minimum level of interoperability.