Author Topic: What's the closest thing to DFDs in UML/EA?  (Read 2189 times)

lipmanc

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What's the closest thing to DFDs in UML/EA?
« on: April 12, 2006, 05:45:02 am »
It seems UML does not do DFDs (data flow diagrams).  What's the closest thing to DFDs in UML/EA?

Kevin Brennan

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Re: What's the closest thing to DFDs in UML/EA?
« Reply #1 on: April 12, 2006, 10:29:14 am »
There is no equivalent--DFDs really have no place in OO modeling (which is what UML is designed for). As a developer friend of mine once said, "data doesn't flow".

The question is more what are you trying to use it for?

If you want to show a process, use an activity diagram, use case, or BPMN model.

For practical purposes, although I know I'm skimming over important theoretical differences, an activity diagram is much the same as a flowchart.

A use case model will show how people use the system to accomplish their goals--it's broadly equivalent to a level 0 DFD.

A BPMN model (available via a plug-in) allows a more expressive description of a business process than an activity diagram.

If you want to show system entities communicating, a sequence diagram might do the trick.

I suspect the first answer is probably better for you, because you can't do a sequence diagram until you understand classes, and if you want to do a DFD, I'm guessing that you're not familiar with OO.



Sr. Consultant at blue sands Inc. and Vice President, Body of Knowledge at the IIBA. All opinions are my own.

jaimeglz

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Re: What's the closest thing to DFDs in UML/EA?
« Reply #2 on: April 16, 2006, 07:45:26 pm »
Hi lipmanc:

I think that what you are looking for is activity diagrams. Be aware that they do have their differences with DFDs; for example, you should use instances of classes (a.k.a. "objects") instead of data stores, and your should use object flow connectors instead of the simple data flow arrows. However, you will find that element variety and syntax are much richer.

The reason why UML did not include DFDs is a long, long story. But, to put it very briefly (and to basically confirm what Kevin is saying): UML is object-oriented, so you need an OO "set of mind", which is very different from the structred modeling frame. However, don't let this intimidate you and, while you become accustomed to the OO world, simply "map" ERDs into class diagrams, and DFDs into activity diagrams.

Hope this helps,

Jaime
« Last Edit: April 16, 2006, 07:48:22 pm by jaimeglz »

Paolo F Cantoni

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Re: What's the closest thing to DFDs in UML/EA?
« Reply #3 on: April 18, 2006, 04:20:57 pm »
Quote
There is no equivalent--DFDs really have no place in OO modeling (which is what UML is designed for). As a developer friend of mine once said, "data doesn't flow".
Hi Kevin,
While your developer friend is technically correct, the observation, to me, seems a bit simplistic.

While the data doesn't flow, the facts represented by the data do "flow" (as per the dictionary definition).  The act of assignment creates a flow of a "fact" from the RValue to the LValue.

The ObjectFlow within UML has these types of characteristics: An object flow is an activity edge that can have objects or data passing along it.  As your friend observed, the objects don't actually flow, but the facts they represent do.  In fact, the [size=13]Superstructure[/size] Specification goes on to say... An object flow models the flow of values to or from object nodes.  The values (in association with the object feature) are the "facts".

My AU$0.05

Paolo
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thomaskilian

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Re: What's the closest thing to DFDs in UML/EA?
« Reply #4 on: April 20, 2006, 04:16:51 pm »
Quote
 The act of assignment creates a flow of a "fact" from the RValue to the LValue.

If that is true, then RValue is lost after it has "flown" to LValue ::)

I always wondered where all these black holes in my computers came from. Now I know 8)

sargasso

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Re: What's the closest thing to DFDs in UML/EA?
« Reply #5 on: April 20, 2006, 04:56:03 pm »
Quote
RValue is lost after it has "flown" to LValue
not necessarily.  The object flow is considered as a finite token, the sending object "places" the token on the flow and the receiving object "detects the presence of" that token.  what each of these objects does regarding its own knowledge of the information it places "within" the token is entirely a matter for that object alone.
Unlike matter, IMO, information can be created and destroyed, but destruction must be an act of volition.  In line with this, the object flow does not physically move an information object from one thing to another, it merely provides a path upon which the sender can place a token and from which the receiver can detect the presence of the token.
Consier the old practical joke of glueing a (fake) $50 note to the bottom of your shoe so it is plainly visible and then standing in the supermarket and observing how other people react.  When you walk off the note is still in the possession of the sender....

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jhawn

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Re: What's the closest thing to DFDs in UML/EA?
« Reply #6 on: June 12, 2006, 01:25:22 pm »
I've been trying to learn EA recently.  I am working as the business analyst between the customer and the software development house.  The software development house doesn't have much in the way of processes yet so I try to comply with what ever they ask for when it supports process structure.  They have ask for me to use UML.  They have a few people who know what it is, but not much experience.  

They also have asked for DFD's.  I have used the activity diagram and anotated it with data flows down to the field level since I know this at this point.  Technically we should be far up front of this, but there is a lot of information I know that has to be passed on to a group that appears to be trying to get their act together.

You might try attaching text or notes to actions or activities and see if that will satisfy your customer and help out.

Jan

jeshaw2

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Re: What's the closest thing to DFDs in UML/EA?
« Reply #7 on: June 12, 2006, 08:39:47 pm »
Effective communication takes priority over standards compliance.  Perfect utterances in the grammar and syntax a given language is not effective if the listener does not understand that language.
Verbal Use Cases aren't worth the paper they are written upon.

SB57

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Re: What's the closest thing to DFDs in UML/EA?
« Reply #8 on: June 19, 2006, 05:04:56 pm »
Hi

I have had the same issue regarding mapping of business process flows and have since found that use of activity diagrams within swim lanes is a good solution.

DFD's are great for a overall perspective, but in the essence of OO, activity diagrams, with a detailed description within and FRS, can work

Cheers
Cheers

lipmanc

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Re: What's the closest thing to DFDs in UML/EA?
« Reply #9 on: June 20, 2006, 05:20:21 pm »
Quote
Hi

I have had the same issue regarding mapping of business process flows and have since found that use of activity diagrams within swim lanes is a good solution.

DFD's are great for a overall perspective, but in the essence of OO, activity diagrams, with a detailed description within and FRS, can work

Cheers


Cool.  I'd like to see how that looks/works.  Would you mind forwarding me a good sample (Sparx@ihood.org)?