Businesses have long dealt with each other by exchanging documents
Halfat's clay pot receipt for taxes is certainly one of the oldest business documents (355 BCE)
The technology for business documents has changed throughout history; we don't use pottery or papyrus or parchment any more, but the basic idea of document exchange has changed relatively little
Document exchange is a very natural thing to do; the simplest case is "here's my catalog, do you want to buy anything" and the exchanged document being "here's my order"
The two-party document exchange pattern is the building block from which more complex patterns are created
