Using an approximation theory approach, we prove that a scaling functi
on l with suitable polynomial decay satisfies the Strang-Fix condition
of order r is an element of N if and only if the elements of any prew
avelet set {psi v}(v is an element of E), with polynomial decay of th
e same order have vanishing integral moments up to order r-1. An analo
gous equivalence is established that does not involve any assumptions
concerning decay; this yields a new characterization of the rate of L-
2-approximation of (stationary and nonstationary) multiresolution anal
yses in terms of a corresponding prewavelet set. Furthermore, we show
that the existence of a scaling Function with polynomial decay implies
the existence of both an orthonormal scaling function and a wavelet s
et with polynomial decay of the same order. Several known construction
s of wavelets and prewavelets are discussed in this respect. (C) 1997
Academic Press.