  The physics programme for a coming electron linear collider is dominated by
events with final states containing many jets. We develop in this paper the
opinion that the best approach is to optimise the independent measurement of
the tracks in the tracker, the photons in the electromagnetic calorimeter and
the neutral hadrons in the camorimetry, together with a good lepton
identification. This can be achieved with a high granularity calorimetry
providing particle separation, through an efficient energy flow algorithm.
