In this paper we present a definition of s-computability for functions in S
obolev spaces HS(Rd), s is an element of R. Two applications of s-computabi
lity are then discussed. One is to address several open problems regarding
classical computable functions; the other is to conduct computable analysis
of several important classes of partial differential equations. (C) 1999 E
lsevier Science B.V. All rights reserved.