Talk:Data-flow diagram

Clean up
I started trying to clean up the article -- I think it was a rough translation from German.
 * Nope, this is just me trying to convey the information that i know is correct, but am not allowed to just copy and paste... Beta m (talk)

I think it's quite good, it just needs some examples that my school might be able to provide.(Contact Rossmoyne Senior High School in Perth Australia)

Sat Apr 30 23:40:07 BST 2011 : edit sjs205

Although in the context diagram the system is sometimes labelled as process 0, it is NEVER referred to as a Level 0 diagram. Subsequently, you "explode" from the context diagram into the level 0 diagram. Processes in a level 0 diagram will always have processes labelled with integers; process 1,2,3... A level 1 diagram would represent a single process contained within a level 0 diagram, and as such, if we were representing process 2 from the level 0 diagram we would label the processes in the level 1 diagram: 2.1, 2.2, 2.3, 2.... Sjs205 (talk) 22:55, 30 April 2011 (UTC)

Example might be needed
Maybe someone should give an example where some c code (or code in another language)can be transformed into a DFD

Add example for DFD

C Code is logical and can easily be converted to a logic flow. Data Flow is the movement of data between entities and the processes that are used to accomplish that. Think of each process as a black box. The inputs are the flows into the process and the outputs are the flows out of the process. Eventually the flows arrive at an entity (Person, Department, Customer, System, etc...) —Preceding unsigned comment added by 63.226.136.254 (talk) 13:05, 23 July 2009 (UTC)

Removed
Removed *Chapter from a book by Edward Yourdon Because it is a broken link.

Attempt to improve the page
I've attempted to start improving this page and work towards removing the clean-up tag. Any suggestions or additions would be much appreciated. Ranglin 06:19, 4 November 2005 (UTC)

some information about DFD Documentation should be useful, as in how to document, what is needed etc... Rey81 (talk) 19:06, 6 September 2008 (UTC)

Merging
I think it is pretty obvious it should be merged with Data_Flow_Diagram. Lewispb 10:33, 4 April 2006 (UTC)
 * I'll tag it. Melchoir 23:29, 13 April 2006 (UTC)


 * Agreed. There's a lot I could write on this too... — Phil Welch (t) (c) 23:45, 1 May 2006 (UTC)


 * Who's going to do the merging? If I can find some free time I'll have a go. TerrorBite 04:50, 4 May 2006 (UTC)


 * Done. Albanaco 18:48, 9 May 2006 (UTC)

An article about a diagram without a diagram!
Can someone who knows the correct symbols etc. make a complete data flow diagram, including as many of the standard symbols as possible, and add it to the top, or near top of the article - it seems stupid to try to describe a diagram without an actual example to look at!--Wierdy1024 22:19, 4 June 2006 (UTC)
 * I was planning to do that, but I'm a bit swamped with life right now. If no one beats me to it, I'll write up a DFD about Wikipedia, and post it to Wikipedia. — Philwelch t 02:05, 5 June 2006 (UTC)
 * That would be awesome Philwelch, if you could squeeze out the time...Regards to all--The world salutes the Rising Star...Try to be One 14:01, 8 December 2006 (UTC)
 * A DFD of Wikipedia? Hoo-boy, "That way lies insanity!"  ;-)  But as a non-expert, knowledge-seeking passerby, I too notice the irony of an article about a diagram without a diagram.  Ditto for the Activity diagram stub that user 202.92.102.220 mentions below.  Fortunately, the references have some diagrams.
 * Kkken 11:37, 14 January 2007 (UTC)

123 — Preceding unsigned comment added by 119.226.62.46 (talk) 06:57, 28 November 2011 (UTC)

Criticism of DFDs
Perhaps we should include a section on the problems/limitations of using DFDs for system analysis and design. A reference to use cases, activity diagrams as a better solution?


 * Good idea, if it could be kept brief, encyclopedic, and NPOV.  Like the pros/cons sections in the use cases article.  Bad idea if it just turns such a section (and this Talk page) into a Hyde Park of rhetoric and debate.  I've actually seen people get hot under the collar on subjects like DFDs.


 * Can you come back to write the problems/limitations section? I see from your contributions page and your Talk page that your IP Address has so many users, it's been blocked unless they each sign in as a member.
 * Kkken 11:37, 14 January 2007 (UTC)


 * The DFD shown here isn't even close to how a DFD works. You're missing the primary purpose of the DFD, and that is to debug requirements.  I will check back and see if I can't help. jim4004  —Preceding unsigned comment added by Jim4004 (talk • contribs) 17:01, 9 December 2008 (UTC)


 * The purpose, and I would say the magic of a DFD, is that it allows an analyst to test their requirements during elicitation. It is unfortunate that it is being viewed as a systems tool.  It's probably one of the better process tools availalble.  It's unfortunate that the name leads people to think that it is meant to only show systems flow.  I have worked with DFD's for over 20 years.  I'd be happy to help with their limitations and otherwise.  I noticed that a Context DFD was omitted because it looked like an IPO chart.  That's what a context DFD looks like.—Jim4004  — Preceding unsigned comment added by Jim4004 (talk • contribs) 20:54, 21 February 2012 (UTC)

Data flow diagram
Real time examples for the data flow diagram for "Top-down approach" and "Event partitioning

approach" will leads to understand the concept well. data flow diagram is useful when we make project —Preceding unsigned comment added by 116.74.114.139 (talk) 04:37, 14 October 2008 (UTC)

Guido De Marco?
What does Guido De Marco, former President of Malta, have to do with structured programming techniques? Could this be a miss-attribution. There is a Thomas (Tom) De Marco, who is well known in data processing and wrote a book "Strurtured Analysis and System Specification", 1978, Yourdon Press. I think that's the De Marco related to this article.

I took a course at UC Berkeley circa 1982 that used his book as a text and it changed my whole outlook on systems development. Tom De Marco deserves a great deal of credit for 'raising the consciousness' of a whole generation of programmer/analysts.

So unless someone can document Guido's contributions to Computer Science, I would like to see this corrected...

Respectfully Yours,

FrejaDog (talk) 21:10, 10 March 2008 (UTC)

I am sure you are right! I have removed some pretty obvious vandalism from the article on Guido de Marco (unless it was an honest misidentification), and also the photo of him in Data_flow_diagram. I am not sure how the Data_flow_diagram article should be updated to give credit to Tom de Marco - I am pretty sure he is not a coauthor of the book, and it looks like there might have been a photo of Tom de Marco at some point, but it was deleted because of fair use problems. Can you fix? Thanks. Jpaulm (talk) 00:07, 11 March 2008 (UTC)

Thanks for responding. I'm sure Guido is also pleased, as is my wife who is part Maltese.

Tom De Marco is the sole author of the the book I'm referring to. The ISBN is 0-13-854380-1. Some how Yourdon Inc has the copywrite but they didn't author the book. I presume that their involvement was financial.

"Structured Analysis and System Specification" by De Marco was published by Prentice Hall as part of their software series. I think that it was one of the earliest books to describe structured analysis using data flow diagrams. An interesting aspect of De Marco's approach is his emphasis on a recursive and iterative style; diagrams are to be drawn only in pencil, shared and discussed, to be used as vehicles of communication and to resist the temptation to treat them as static icons, and, most importantly,  a willingness to 'rip it up' and start over again. Later approaches, such as Yourdon's work, become, in my opinion, entirely too formal and technical, with too much emphasis on the methodology itself.

Most systems people are only familiar with the Yourdon work, and therefore rightly complain that Structured Analysis and Data Flow is too formal and cumbersome to be effectively used in the 'real' world.

Regards, FrejaDog (talk) 16:47, 11 March 2008 (UTC)


 * I probably took the same course at UC Berkeley circa 1982! The textbook used was written by Tom De Marco.  The course literally changed my conceptual world and the way in which I worked!  Yourdon published their version of "Data Flow Diagramming" (Sarson and Gane) at a later date.  In my opinion, the Yourdon version was too formal and missed the key point, the informal and interative focus of the original work. It was a pretty obvious attempt by Yourdon Press to commercialize and differentiate "DFD" as a product.  The complexity, rigidity, and formality of the Yourdon product made it unpopular with management and developers.  Apparently, Yourdon's copyright, extended to cover the whole of DFD, effectively ended further open development of the technique.  Henceforth, DFD would be invariably referred to as 'Sarson and Gane' or 'Yourdon'... Yowoof (talk) 15:48, 27 September 2018 (UTC)

== Inconsistent Elements = I am working on developing some documentation for a system and hit this topic for pointers. One thing I noted is that the elements are defined with certain shapes at the start of the topic, but the shapes used in the actual diagram examples are inconsistent.

The text indicates that processes (functions) are depicted with circles and entities are depicted with rectangles - I believe this is accurate. The example diagrams have these reversed. —Preceding unsigned comment added by Rsbradley (talk • contribs) 17:04, 8 August 2008 (UTC)

Gane and Sarson
Should more information be given to the Gane and Sarson notation as well? 143.89.188.6 (talk) 13:00, 13 October 2008 (UTC)

Data store redirection
I'm not convinced by the redirect of data store to this page (which then doesn't really define data store, even within the context of DFDs). Surely data store would be better served by a specific definition on its own page or else a redirect to database? Furrypop (talk) 14:39, 24 November 2008 (UTC)

New example diagram(s)


I agree we need an example, but the current image diagram isn't appropriate, (the lack of arrowheads is a dead givaway.)  Looking into the comments added above, I see what looks like wikipedia original artwork linked to an article named Event partitioning that looks like a good start. It's really a context diagram, and to really illustrate the point of a DFD well, we would should a level or two below that.

Burt Harris (talk) 04:44, 31 December 2008 (UTC)

Wrong example- Mixing IFD examples in DFD article
The example in the first figure in the introduction is IFD (Information Flow Diagrams) and not DFD. It do not comply with the DFD definitions. It should be added to the IFD article, and be removed from here. The examples within the text are correct. The example by Burt Harris is a Level 0 DFD but is too complex to be a starting point. Ariek (talk) 09:27, 6 March 2009 (UTC) —Preceding unsigned comment added by Ariek (talk • contribs)

Agree completely with the author of this comment - the example at the top of the page is NOT a DFD. DFDs do not have lines connecting processes (yes, IFDs do). The DFD is concerned with showing where data flows from, and to, processes - not how processes are themselves connected. The figure should be replaced as it is incorrect. — Preceding unsigned comment added by 38.140.120.178 (talk) 13:40, 30 March 2016 (UTC)

"dataflow", "data flow" or "data-flow"?
Should it be "dataflow", "data flow" or "data-flow"? This article currently uses all three forms.

"Modern Structured Analysis" (Prentice-Hall, 1989, ISBN 0-13-598632-X) by Edward Yourdon (father of this type of diagram?), and the Structured Analysis Wiki uses "dataflow", the first listed form.

--Mortense (talk) 14:08, 26 July 2010 (UTC)


 * The correct one should be "data flow diagram" based on McGraw Hill Textbook. FYI, data flow diagram is not like writing "use-case diagram" (using dash). Ivan Akira (talk) 11:24, 28 September 2010 (UTC)

The Wikipedia lemmas are devided: dataflow programming and dataflow architecture vs. data flow diagram vs. data-flow analysis. Needless to say, the articles are all inconsistent in their spelling.

The Merriam-Webster dictionary lists only the contracted spelling: dataflow. The Dragon Book, in contrast, uses the hyphen in compounds (e.g., data-flow analysis). So does Steven Muchnick in "Advanced Compiler Design and Implementation", dropping the hyphen outside of compounds (e.g., "data flow is not control flow").

It seems that the programming and architecture communities use the contracted form (dataflow programming and dataflow architecture) whereas the compiler people use a hyphen in compounds and a space otherwise (data-flow analysis, data-flow diagram and data flow). Let's use this spelling consistently throughout the article. --EnOreg (talk) 11:58, 24 January 2011 (UTC)

Copyright problem removed
Prior content in this article duplicated one or more previously published sources. The material was copied from: http://www.getahead-direct.com/gwbadfd.htm. Infringing material has been rewritten or removed and must not be restored, unless it is duly released under a compatible license. (For more information, please see "using copyrighted works from others" if you are not the copyright holder of this material, or "donating copyrighted materials" if you are.) For legal reasons, we cannot accept copyrighted text or images borrowed from other web sites or published material; such additions will be deleted. Contributors may use copyrighted publications as a source of information, but not as a source of sentences or phrases. Accordingly, the material may be rewritten, but only if it does not infringe on the copyright of the original or plagiarize from that source. Please see our guideline on non-free text for how to properly implement limited quotations of copyrighted text. Wikipedia takes copyright violations very seriously, and persistent violators will be blocked from editing. While we appreciate contributions, we must require all contributors to understand and comply with these policies. Thank you. Danger (talk) 15:14, 18 October 2011 (UTC)

Proposed merge with Physical Data Flow
It sound like this (and Logical Data Flow which redirects here) are simply poorly named categories of DFD. If there is any merit to this unreferenced article it should probably be merged. Derek Andrews (talk) 17:50, 28 February 2014 (UTC)
 * Done! Three years later I don't think anyone will object. Triptothecottage (talk) 10:12, 30 January 2017 (UTC)

Assessment comment
Substituted at 12:52, 29 April 2016 (UTC)

cryptographic data flow diagram


The block cipher article seems to be saying that ARX network diagrams used to illustrate block ciphers and hashes -- such as the one on the right -- are a kind of data flow diagram.

Is this type of diagram something that needs to be discussed in this "data flow diagram" article? Or is this type of diagram different enough that discussion needs to go into some other article (that may not yet exist) -- and if so, what is the name of that other article? --DavidCary (talk) 03:18, 31 October 2016 (UTC)

complete redo
Hi all, I completely redid the DFD — Preceding unsigned comment added by Svejdam (talk • contribs) 22:30, 9 January 2019 (UTC)

Terminology and sources
The terminology used in this article would need to be sourced, or aligned with known sources, since it seems not to correspond to the common terminology of DFD:


 * Warehouse: is called "files" by Yourdon/DeMarco, and "data store" by Gane & Sarson
 * Terminator: is called "source or sink" by Yourdon/DeMarco, "external entities" as well as "source or destination" by Gane & Sarson

Some other terms would benefit from being related (e.g. contextual diagram and zero level diagram

In at least one case sourcing is misleading: a sentence is sourced with an article of 1975, but contains some claim about UML, which dates from the 90s.

India Education Program course assignment
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