Events happen in the service user world, and demand a response in the service provider world. Information arrives in the service provider world asynchronously (and unreliably). Messages do not necessarily arrive in the same order as the events they describe, and may be subject to interference.
For example, a credit card operation may receive a range of messages (service requests) from cardholders and others, including charges, payments, disputed charges, notification of lost/stolen cards, updates from credit bureau, bankruptcy or death of cardholder, and more. These messages may be mixed up in various ways. Security and error prevention measures may reduce the frequency of error, but have the effect of further complicating the message traffic.
A traditional service provider will often get tied into knots with errors and exceptions. One of the requirements for SOA service provision is the capability of handling asynchronous and unreliable information. This has organizational implications as well as systems implications.
Extract from CBDi Best Practice Report, January 2004