Summer of Protocols

"The purpose of a system is what it does" :: "The purpose of a protocol is what it _______"?

One of the interesting ideas (see Olivia essay) from SoP was that protocols do not have purposes. Only functions.

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then maybe: 

"The purpose of a system is what it does" :: "The ________ of a protocol is what it does"?

“Disposition” might be a good word. In Extrastatecraft, Keller Easterling argues that urban planning and building protocols have mechanistic “dispositions” (such as homogenization)

A disposition is functional by definition. Often in the form of a “message of the medium.” Regularities induced by the specific uniform way the function is repeatedly fulfilled. Often evident via undersigned emergent shaping of environment and user psyches.