In Schach p. 364, Gane and Sarsen method is used as an example of (graphical) structured system analysis. It is a nine-step process that is used for system specifications and it is quite a popular method. It is a method that is also preferred in industrial software desgn and specifications. However, as I have used it to answer problem 12.20 of Assignment 2, not all things about it are inherently clear. The paragraph below describes these problems and pose questions that will help other students understand Gane and Sarsen's method.

First, Are there different versions of Gane & Sarsen's Method? If there are different versions of the method, which one is the best to use to draw the data flow diagrams. The reason why I am asking these two questions is because I noticed different web applications offer different types of data flow drawing components. For example, an online diagram software called Creately does not use a shadowed square to describe an actor in a DFD diagram. 

Second, does the diagram representing a store of data only represents records found on the database? In an ideal scenario, one finds that a system needs to have temporary data storage points for example caches. Is it correct to regard data dumps and caches as data stores?

Additionally, is it necessary to indicate all iterations of the DFDs in the assignments? The ChocAn system defined in Appendix A of Schach's book takes a number of iterations to come up with the correct DFD diagrams. Do we need to indicate those iterations or only the final versions?

Is there a method to define precise physical resources as required in step 6 of Gane and Sarsen's method (p. 370)? Physical requirements can be defined as database requirements defined down to the record level. However, Schach does not present a way to choose a database system over another. Therefore, it leaves a leeway for using any format to define the database system for the ChocAn system.

How can one go about step 8 & 9 of Gane and Sarsen's method as applied for the Chocoholics Anonymous System (p. 371 & 627)? The two steps look a bit technique since they entail calculating the amount of system requirements required for an application. Is there a formula for calculating the requirements such as memory space, bandwidth etc?

Source: Schach, S.R. 2011. Object-Oriented & Classical Software Engineering. New York: McGraw Hill.