The general classification of K-operators describes the scheme as shown in Figure , where IKO stands for ``integral K-operators'', DKO for ``differential K-operators'', and PDKO for ``pseudo differential K-operators''.

This scheme does not describe
numerical methods but only the way in which a K-operator is introduced.
The fact that the circles intersect, shows that different definitions can
determine the same operator.^{} Due to the three numerical representations of
the operators, we have three classes of algorithms: stacking(integration),
finite difference techniques in the -domain, and continuation in the
-domain.

1/13/1998