4

Is it allowed to create a conditional statement in DFD? Is there a need to show validation and conditional statements when making a DFD or its just the flow of data?

Like for example, when creating a DFD for a login page in a web-based application, am I going to show if the user is valid or not?

Adan
  • 147
  • 2
  • 2
  • 14
  • yes you must have a proper flow within the data,, suppose the data is wrong the flow may not be good . so in that time triggering a error should be there . so to have a good DFD needs all workflows from top to bottom – Sam Arul Raj T Feb 20 '12 at 09:39
  • Wouldn't it look like a Flow Chart if I added conditions in my DFD? – Adan Feb 20 '12 at 09:49

2 Answers2

1

In general DFDs do not show conditionals as such, neither do they show the location where a process is executed or the sequence of operations. You need to see DFDs like functions, which return something based on their input parameters.

A login screen would then most likely be a process which reads user credentials and returns a user-id or nothing in case the user is invalid. You may see two outgoing flows in cases you want to do something special in case the user is invalid. Or it may return a reason why a user is invalid (unknown user, wrong password, account expired). Clarifying these things is the purpose of DFD modelling, so the answers depend on your project.

In general one must resist the temptation to add too much detail to DFDs.

Martin Drautzburg
  • 5,143
  • 1
  • 27
  • 39
1

I think that what you asking is called Transaction Flow. Basically, you use a transaction that triggers the data flow along a path. Roger. S. Pressman defines it with an example.

Software Engineering: A Practitioner's Approach.6th edition Chapter 10.6.2.

https://books.google.es/books?id=bL7QZHtWvaUC&lpg=PR13&ots=O6v89MxK8l&dq=pressman%2010.6.2&hl=es&pg=PA276#v=onepage&q=pressman%2010.6.2&f=false

Dondani
  • 74
  • 8
  • While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes. – David Faber Jan 17 '15 at 20:59
  • The essential part is in the answer. I didn't want to copy-paste a chapter and an image from a book. I can delete the link, and keep the reference. – Dondani Jan 17 '15 at 22:31