This paper investigates what kinds of information are necessary and sufficient to design and evaluate image processing software programs and proposes a representation of these information elements using a computational language performable by vision systems and understandable by experts. The language is built upon a formulation model which distinguishes the specification of a goal and the definition of an input image class. Goals are stated in terms of tasks together with result samples. Image classes are defined by both linguistic and iconic descriptions. The model is implemented as an OWL domain ontology which provides the primitives for the formulation language.