We will close this issue but add faults to the spec to handle invalid concurrent operations

I think that this issue is largely resolved in the specifications submitted for GGF11.  In essence, as there are no longer OGSI Service instances 
representing sessions, the WS-DAI spec states that the default is multi-user, with some form of context mechanism grouping requests.  There is also a 
behavioral property that can indicate if concurrent access is not supported. I suspect that  the consequences of stating that it is not are not 
explicit - for example, should the message fault? This is not in the WS-DAI spec, due to the lack of operations there.  Perhaps faults that result 
from behavioral properties should be included in the WS-DAI specification.