This paper introduces a new kind of evolutionary method, called "skeletal algorithm", and shows its sample application to process mining. The basic idea behind the skeletal algorithm is to express a problem in terms of congruences on a structure, build an initial set of congruences, and improve it by taking limited unions/intersections, until a suitable condition is reached. Skeletal algorithms naturally arise in the context of data/process minig, where the skeleton is the "free" structure on initial data and a congruence corresponds to similarities in data. In such a context, skeletal algorithms come equipped with fitness functions measuring the complexity of a model. We examine two fitness functions for our sample problem-one based on Minimum Description Length Principle, and the other based on Bayesian Interpretation. • an observable action of the event; we shall assume, that we are given only some rough information about the real actions. and we shall forget about any additional information