Re: Data Flow Diagrams

Subject: Re: Data Flow Diagrams
From: "Anthony Markatos" <tonymar -at- hotmail -dot- com>
To: chris -at- bdk -dot- net, tonymar -at- hotmail -dot- com
Date: Thu, 13 Jan 2000 17:28:37 PST

Chris Kowalchuk said:

Let me first say that I too, as a tech writer who sometimes helps
develop software specs, typically resort to data flow diagrams. Whenever I do, the programmers are amazed.....

Tony Markatos responds:

Wow! - there are at least two others on this planet who create DFDs (you and Win). What a feeling! - I am not alone! :-)

Chris Kowalchuk said:

[Computer programmers do not create DFDs because] ........Computer programming has a long history of being approached from a "just make it work" attitude....

[But (software) engineers do create DFDs because] ..... an engineer who could not do a proper spec or map out a process would probably not make it out of engineer school.

Tony Markatos:

First let me emphasize that I am talking about REAL Data Flow Diagrams, not "poor-man" imitations - often called things like Process Flow Diagrams, Process Diagrams, Flow Diagrams, etc.

Now to comment on your comment: The older I get, the truer rings the old saying "Believe none of what you hear and only half of what you see." And, while your comment logically makes sense, it contradicts what I have seen.

I have, as a business analyst type, lead (larger-scale) requirements specification projects which included "engineers" having Phds in IT from MIT and Stanford (and a Harvard MBA type, but he don't count). These guys were sharp, like real sharp - except when the need was to create Data Flow Diagrams. Then, mysterious things would always happen, and I would, inevitably, be the only one doing them. They were "hungry" for my output, but I was the only DFDer.

At one(a large Southern California aerospace) company, I was a member of an elite DFD "gruppie" department. (I was drafted into it - I don't "gruppie" anything.) These people ate, slept, and breathed DFDs. They constantly talked about the benefit of them. They developed a large in-house library on them. They taught evening courses in them. One guy - a real "borne-again Christian" type - would often loudly quote famous passages from DeMarco and Yourdon (famous DFD authors). But, funny thing, when it came time to actually do DFDs (like for work); I was, once again, alone.

So maybe you have worked with engineers who create DFDs. If so, then I have only worked poorer-quality companies (Note: I have worked coast-to-coast, large-medium-small, and for several international consulting companys.)

Don't get me wrong Chris, I am definetly pro-DFD (and other SSAD techniques). Properly used they are, as it sounds like you have discovered, very powerful.

I think that a major reason for there gross underutilization has been the way they were taught. Example: Yourdon used to say that DFDs without an accompanying data dictionary were merely "rough-sketches". This scares people. For in the final analysis, Structured Systems Analysis is merely rigorously enforced honesty. And the human capacity for honesty is limited - increasing I think, but still limited.

Tony Markatos
(tonymar -at- hotmail -dot- com)

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