An approach of constructing isospectral flows K-l, nonisospectral flow
s sigma(k) and their implicit representations of a general Lax integra
ble system is proposed. By introducing product function matrices, it i
s shown that the two sets of flows and of related symmetries both cons
titute infinite-dimensional Lie algebras with respect to the commutato
r [.,.] given in this paper. Algebraic properties for some well-known
integrable systems such as the AKNS system, the generalized Harry Dym
system, and the n-wave interaction system are obtained as particular e
xamples. (C) 1996 American Institute of Physics.