The algorithmic way of processing and analysing digital images has developed powerful means to interpret specified kinds of images, but failed in providing general image understanding methods that work on all kinds of images. Declarative Knowledge We differentiate between procedural and declarative knowledge. Procedural knowledege is typically incorporated in an algorithm or a program, whereas declarative knowledge is represented expicitly and symbolically and should be independent of the methods to perform inferences on it. Thus, by using declarative knowledge representations we gain flexibility and lose efficiency. For the several processing steps we need different kinds of knowledge.
Image understanding is a goal-directed activity.
More or less a detailed german version of this survey focusing a bit on the medical aspects of image understanding.