Standards considered part of the first-generation Web Services framework are WSDL, SOAP, UDDI. (These, of course, rely on pre-existing standards, such as XML, XML Schema and HTTP.)
There are many second-generation standards that have surfaced, each addressing a specific extension to the first-generation framework. These specifications are often referred to as WS-* standards, because most of them are prefixed with "WS-". The development of most of these standards was driven by major software manufacturers, many of which collaborated. Some standards have been widely accepted, while others failed to gain any support.
There are too many to list here, but some of the key (and more established) WS-* specifications that
you should be aware of include:
- WS-Coordination (for context management)
- WS-AtomicTransaction (for ACID transaction support)
- WS-BusinessActivity (for long-running transactions w/o rollback)
- BPEL4WS (for orchestration workflow logic)
- WS-Security (a framework of standards governing Web services security)
- WS-ReliableMessaging (for message acknowledgement and delivery failure reporting)
If you would like to learn more about any of these specifications, have a look at
http://www.ws-standards.com/ and check out
http://www.specifications.ws/ for links to the actual specifications. The ws-standards site also contains a diagram that illustrates how these standards inter-relate.