The European Large Area ISO Survey - I. Goals, definition and observations by Oliver, S, Rowan-Robinson, M, Alexander, D, Almaini, O, Balcells, M, Baker, A, Barcons, X, Barden, M, Bellas-Velidis, I, Cabrera-Guerra, F, Carballo, R, Cesarsky, C, Ciliegi, P, Clements, D, Crockett, H, Danese, L, Dapergolas, A, Drolias, B, Eaton, N, Efstathiou, A, Egami, E, Elbaz, D, Fadda, D, Fox, M, Franceschini, A