Program slicing is a useful analysis for aiding differentsoftware engineering activities. In the past decades, various notionsof program slices have been evolved as well as a number of methods tocompute them. By now program slicing has numerous applications insoftware maintenance, program comprehension, reverse engineering,program integration, and software testing. Usability of program slicingfor real world programs depends on many factors such as precision,speed, and scalability, which have already been addressed in theliterature. However, only a little attention has been brought to thepractical demand: when the slices are large or difficult to understand,which often occur in the case of larger programs, how to give anexplanation for the user why a particular element has been includedin the resulting slice. This paper describes a reasoning method aboutelements of static program slices.