WebServices.Org covers yet another spec for the WS- bucket: WS-Reliability:
The purpose of WS-Reliability is to address reliable messaging requirements, which become critical, for example, when using Web Services in B2B applications. SOAP [SOAP1.1] over HTTP [RFC2616] is not sufficient when an application-level messaging protocol must also address reliability and security. While security is getting traction in the development of Web Services standards, reliability is not. This specification is intended as an initial proposal for defining reliability in the conte xt of current Web Services standards. The specification borrows from previous work in messaging and transport protocols, e.g., SOAP, and the ebXML Message Service [ebMS]. It proposes appropriate modifications to apply this work to Web Services.