What is a Enterprise Service Bus, how is it diffenet from a Message Bus. IF you look at all MOMs currently in the market, they seem to some kind of Message Bus. May be with some WS* support.

I know ESB is a concept. When will you term a framework/solution to be an ESB? I was referring to a blog by Boby Woolf, who says

1. Services in an ESB should be self describing.
2. An ESB client will be able to query the ESB to ask it what services it hosts??

But he confuses the whole stuff with lot of Web Services stacks like WSDL and UDDI.


Any thoughts??