It is important to determine what context of use is to be taken into consideration in the evaluation. Whilst it is impossible to give a detailed breakdown of all possible contexts of use, an example may help to clarify what is meant here.
Example. Imagine an MT system as one component in a system whose overall purpose is to retrieve and present to the user information on railway timetables, accepting voice input and producing voice output. The boundaries could be taken as:
(a) actual speakers receiving actual information; (b) the MT system receiving artificially constructed transcribed input on one side and the spoken output on the other; (c) the MT system receiving artificially transcribed input and producing as output the input to the speech synthesizer; (d) the MT system receiving artificially transcribed input and producing a query to the timetable query system; (e) the MT system receiving information from the timetable query system and generating from it the input to the speech synthesizer;
It can readily be seen that many other possibilities exist, especially if we widen the boundary even further to include different types of end users and different places where the system may be installed. This notion is closely related to the notion of set-up discussed in Sparck Jones.