The aim of program analysis and visualisation (PA&V) is to help the programmer understand a program by means of graphical presentations of different aspects of the program. Program analysis and visualisation systems can be classified according to the specification method of visualisation, e.g., in what way can the user of the system specify his own visualisers. In the article three specification methods (predefinition, annotation and declaration) are discussed and some example systems are presented. Particular attention is paid to the declarative specification method, thus, in addition, knowledge-based program analysers are discussed. Increased understandability and modifiability are argued to be the main advantages of declarative PA&V systems.

The general discussion is continued by a short presentation of a case study, where the declarative and synthesisable visualisation in the NUT system is discussed.