About CRUD on DFD


===I’m copying this from my another blog. ===

ModernSystemAnalysis

I am reading this book recently. Sometimes I’m confuse when creating DFD. Some questions always flying in my head. This is some notes came from the books which i highlight it. It means very important!

  1. Chapter 7, page 214.
  • A data flow to a data store means update (delete or change)
  • A data flow from a data store means retrieve or use

2. Chapter 7, page 212-213

“Notice that the sources/sinks are the same in the context diagram and in this diagram: the customer, the kitchen, and the restaurant’s manager. This diagram is called A LEVEL 0 DIAGRAM because it represents the primary individual processes in the system at the highest possible level. Each process has a number that ends in .0 (CORRESPONDING TO THE LEVEL NUMBER of THE DFD)”

3. Chapter 7, page 217

As a rule of thumb, no DFD should have more than about SEVEN processes, because too many processes will make the diagram too crowded and difficult to understand.

4. Chapter 7, page 218

Many times, students just learning DFDs will use the names of people who perform the process or the department in which the process is performed as the process name. THIS practice is not very useful, because we are more interested IN THE ACTION the PROCESS REPRESENTS than THE PERSON PERFORMING it or the place where it occurs.

  1. Chapter 7 page 216

Decomposition continues until you have reached the point at which no subprocess can logically be broken down any further. The lowest level of a DFD is called a primitive DFD

  1. Chapter 7, page 227

More concrete rules for when to stop decomposing are:

When you have reduced each process to a single decision or calculation or to a single database operation, such as RETRIEVE, UPDATE, CREATE, DELETE or READ


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