The Jackson Program Design Methodology, sometimes called Jackson Structured Programming (JSP), is a method for program design and modelling "in the small". It begins with considerations about what is known and develops a program design that becomes more complete as the model is put through continued iterations. It emerged in the 1970's as a design method that concentrated on the structure of data using data-structure methods. Because it builds the program design from an incomplete model, it is termed a "composition type" method. 

See http://www.soc.staffs.ac.uk/~cmtkch/teaching/cds/level_2/sep/supplemental/jsp/jackson%20structured%20programming.htm  ''(BrokenLink - 2004-04-14)''

In today's terminology JacksonSP was a method to split the iterator code and the application specific composite / visitor code. (JimCaprioli)

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See also: ProceduralMethodologies