Promises as a basis for payments

Andrew Bransford Brown asks:

• Can all financial transactions can be described as:

One promise for another.
Did each side deliver?

Abbreviated example of a banking protocol:

 transaction
   promise
     1USD
   endpromise
   promise
     1 pack of gum
   endpromise
 endtransaction

• Why the word "promise"? Because "promise" connotes time. There is no such thing as an "instantaneous transaction".

• Further details in Promise Language