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