8: CLASSIFICATION OF K-OPERATORS

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 $({\bf r},t)$-domain, and continuation in the $(\omega,{\bf k})$-domain.