Re: Proposed text on reliability in the web services architecture

Peter Furniss wrote,
> The cure, as Miles says, is to get the assurance of processing from
> the processor, not from the intermediary.

Agreed.

But the crux of my mail was that an endpoint WS node might effectively 
be an intermediary if it's acting as a gateway to a non-WS "legacy" 
system. These kinds of adapters are surely very common, and likely to 
stay that way for the foreseeable future.

The problem is that arranging for those backend systems to signal a 
failure back to the gateway, so the later can provide a nack back as 
part of a WS reliable messaging protocol, might be difficult or 
impossible. So if the gateway sends an ack back to the sender it could 
be misreporting a failure as a success ... hence the connection with 
byzantine failures.

I think the right think to do here is to allow a node a "can't say" 
option in addition to ack and nack, and probably allow the sender to 
require an ack or a nack (ie. if a gateway node can't guarantee either 
it should return a fault).

Cheers,


Miles