REST has rapidly been displacing SOAP as the pragmatic choice for accessing and interacting with resources over HTTP.

The SOAP protocol is too unwieldy and cumbersome for all but the most heavily engineered situations. (The S in SOAP was originally supposed to stand for simple, but was changed to service as it was considered to be misleading).

So just as we are all getting used to using REST to implement web-services along comes a new acronym MEST.

MEST stands for MESsage Transfer or Message Exchange State Transferand is to service oriented architectures what REST is to resource oriented architectures. REST enables you to interact with the objects and properties that make up resources, while MEST enables you to send messages and invoke services. The people behind the MEST do not make any more claims for it than this, it's a message to a service in the same way that that a REST operation is just access to and manipulation of a resource.

I don't think it's rocket science, and most of us have probably been doing this kind of thing all along, but sometimes it's useful to attach a label just because it makes it easier to talk about and explain.