As background we first need a generic distinction between content and format.
Imagine you are in an unfamiliar city and are trying to get to the central station.
A stranger offers you two routes. Each route could be represented by a distinct line
on a paper map. The difference between the two lines is a difference in content.
Each of the routes could alternatively have been represented by a distinct series
of instructions written on the same piece of paper; these cartographic and
propositional representations differ in format. The format of a representation
constrains its possible contents. For example, a representation with a cartographic
format cannot represent what is represented by sentences such as `There could not be a
mountain whose summit is inaccessible.'\footnote{ Note that the distinction between
content and format is orthogonal to issues about representational medium. The maps in
our illustration may be paper map or electronic maps, and the instructions may be spoken,
signed or written. This difference is one of medium.} The distinction between content and
format is necessary because, as our illustration shows, each can be varied independently
of the other.
Format matters because only where two representations have the same format can they be straightforwardly inferentially integrated.
To illustrate, let’s stay with representations of routes.
Suppose you are given some verbal instructions describing a route. You are then shown a representation of a route on a map and asked whether this is the same route that was verbally described. You are not allowed to find out by following the routes or by imagining following them.
Special cases aside, answering the question will involve a process of translation because two distinct representational formats are involved, propositional and cartographic. It is not be enough that you could follow either representation of the route. You will also need to be able to translate from at least one representational format into at least one other format.