> If you think about verbs as messages (data), then you would simply POST a make_sale(product, customer) message to some URL
I would say instead that if you were thinking in actions-as-domain-resources, then you would post a "sale(product, customer)" entity to a "sales" collection resource (via POST to the appropriate URL, in an HTTP API) -- which is pretty much the same thing, though not calling it "make_sale" is more REST-appropriate; the combination of the operation and the resource should make the "make" part superfluous.
I would say instead that if you were thinking in actions-as-domain-resources, then you would post a "sale(product, customer)" entity to a "sales" collection resource (via POST to the appropriate URL, in an HTTP API) -- which is pretty much the same thing, though not calling it "make_sale" is more REST-appropriate; the combination of the operation and the resource should make the "make" part superfluous.