Author Topic: Using an element more than once on a diagram  (Read 2319 times)

beginner

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Re: Using an element more than once on a diagram
« Reply #15 on: November 04, 2009, 03:21:08 am »
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Oh, this issue again ;D

...Remove the diagrams from a model and you have not lost anything (except for a convenient way to communicate its contents to Humans)
...
Haha. Remove the characters from a book and you still have a book.

UML is a LANGUAGE and thus is for COMMUNICATION. That's what it's all about. Diagrams are MAJOR part of it all.

b.

g.makulik

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Re: Using an element more than once on a diagram
« Reply #16 on: November 04, 2009, 04:53:52 am »
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Haha. Remove the characters from a book and you still have a book.
No. Its the other way round: The model contents (as you can see e.g. in EAs project view) are the books characters. Removing the diagrams from the model, would be more like bathing the book in ink so that its not very readable anymore.

Just my 0.02 EUR
Günther
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Geert Bellekens

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Re: Using an element more than once on a diagram
« Reply #17 on: November 04, 2009, 07:18:51 am »
Or like removing the monitor from a computer.
You still have everything in there, and it is perfectly usable for other computers. Only humans will have a hard time reading what you have on the computer because they can't interprete binary electrical signals.

Geert

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Re: Using an element more than once on a diagram
« Reply #18 on: November 04, 2009, 07:22:23 am »
What are you talking about??? UML is for communicating with HUMANS, not COMPUTERS. Maybe I'm on the wrong planet here.  :(

b.

Simon M

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Re: Using an element more than once on a diagram
« Reply #19 on: November 04, 2009, 08:35:32 am »
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Well, my point of view is that EA is not fully UML compliant because it doesn't allow multiple representations of the same element on a diagram.

...

That is the reason why there are no rules for diagrams. There might be "best-practices" that tell us not to represent an element twice on a diagram, but no rules.
If there are no rules, then how can EA be non-compliant based on what it does with diagrams?

The UML spec does talk about diagrams quite a bit.  It gives a lot of options for how you may want to render things.  Although it shows some classes on the one diagram multiple times, I'm not aware of anywhere that it says a tool must provide that capability.  On the other hand, I do know one place where it specifically says (or used to) that many diagrams in the spec do not conform.  (The conventions used for owned association ends and navigability)

So, although it may useful in some cases.  I don't see that any UML tool has to provide support for showing the same element more than once on a diagram.
Simon

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g.makulik

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Re: Using an element more than once on a diagram
« Reply #20 on: November 04, 2009, 08:43:24 am »
... and since UML lacks of a notation for indicating an element that appears more than once at the same diagram, stick with it. It's good as it is IMHO.

Günther
Using EA9.3, UML2.3, C++, linux, my brain, http://makulik.github.com/sttcl/

g.makulik

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Re: Using an element more than once on a diagram
« Reply #21 on: November 04, 2009, 08:51:59 am »
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UML is for communicating with HUMANS
No, that's just one of it's purposes in IT technolgy. UML serves far more, involving communication with computers (programs).

Quote
Maybe I'm on the wrong planet here.  :(
Sorry, I guess you have been shipwrecked in the wrong universe ...

Dont rant, learn young padwan! ;)

Günther

PS.: Stop shouting please.


« Last Edit: November 04, 2009, 08:52:47 am by g.makulik »
Using EA9.3, UML2.3, C++, linux, my brain, http://makulik.github.com/sttcl/

KP

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Re: Using an element more than once on a diagram
« Reply #22 on: November 04, 2009, 08:59:11 am »
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What are you talking about??? UML is for communicating with HUMANS, not COMPUTERS. Maybe I'm on the wrong planet here.  :(

b.
Plenty of people create UML models with computers as the primary target audience, e.g. for code generation. However, it helps if the models are also human readable :)
The Sparx Team
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Geert Bellekens

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Re: Using an element more than once on a diagram
« Reply #23 on: November 04, 2009, 06:20:19 pm »
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... and since UML lacks of a notation for indicating an element that appears more than once at the same diagram, stick with it. It's good as it is IMHO.

No, I don't think it is good as it is. UML enforces enough rules as it is, and I don't want my modelling tool to add some arbitrary rules.
The tool should give me all the freedom possible to model within the boundaries of UML (and beyond, it's used for other modelling languages as well!).
If for some reason I can communicate the model better with a diagram that contains multiple representations of the same element, then EA should allow that.

I think the reason EA doesn't support this is because the constraint of one representation per element is embedded in the heart of their design. Changing this might prove to be a difficult excercise.

Geert

beginner

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Re: Using an element more than once on a diagram
« Reply #24 on: November 04, 2009, 07:19:00 pm »
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Quote
What are you talking about??? UML is for communicating with HUMANS, not COMPUTERS. Maybe I'm on the wrong planet here.  :(

b.
Plenty of people create UML models with computers as the primary target audience, e.g. for code generation. However, it helps if the models are also human readable :)
It helps 0.0 if humans can't read it. In many cases it's even contra-productive. The inability to communicate comes from what people "assume" as the "meaning" of things. This "meaning" is what can be called "common sense". But what is "common sense". Where you have just 2 differentiations of snow an Inuit has a hundred.

First thing to learn: communicate so your partner "understands" what you are trying to tell. When using UML there might be common sense between hard core users in many aspects. Obviously there is some terra incognita. Talking with UML newbies you have to be extra careful. In order to avoid communication problems the problem of rendering the same thing differently will open the door for misunderstandings. One should find a way out of this dilemma.

b.

P.S. I will contemplate, Darth G.

Geert Bellekens

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Re: Using an element more than once on a diagram
« Reply #25 on: November 04, 2009, 07:37:38 pm »
I think no-one (especially not me) is trying to say that we don't need diagrams.
My only point is that the diagram should be a view on the model and should not contain (model) information.

Another analogy is the GUI/Database in a typical application.
I see the diagrams as the GUI, the the model as the database.
Surely we could work with an application without a GUI by directly editing the database, but it would be very practical.
We however never store information in the GUI. Everything is stored in the database, and the GUI just provides a (human readable) view on this information.

Geert

beginner

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Re: Using an element more than once on a diagram
« Reply #26 on: November 04, 2009, 08:27:01 pm »
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... the GUI just provides a (human readable) view on this information...
Fully agree if you omit "just". Of course the model is still the model without the view, but it is of no worth if you can't understand it. And we humans DO need a (G)UI to UNDERSTAND. That's why I emphasize on this aspect!

b.

Makulik

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Re: Using an element more than once on a diagram
« Reply #27 on: November 04, 2009, 09:37:16 pm »
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P.S. I will contemplate, Darth G.
[off_topic]
Ooops, I always felt being on the Jedis side using 'The Force'. But good, do so.

Why are you still shouting? Usually this indicates for me, s.o. tries to overcome his lacking of arguments or knowledge in a discussion, insisting he's right. Some people might find this a bit offending. If you want to emphasize on s.th. I think it's fairly enough to emphasize the text, instead of shouting (i.e. using capital letters).
[/off_topic]

Günther

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Re: Using an element more than once on a diagram
« Reply #28 on: November 04, 2009, 09:52:41 pm »
The Dark Force is always south of the "Weißwurschtäquator"

And sorry for emphasizing THIS way. The circuit for bold face on my VT100 is defective.

b.

son-of-sargasso

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Re: Using an element more than once on a diagram
« Reply #29 on: November 04, 2009, 10:45:49 pm »
Simon said:
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Although it shows some classes on the one diagram multiple times, I'm not aware of anywhere that it says a tool must provide that capability.
 which is quite correct.  However, I'll say it again and again and again, UML does say anything in with the same name in the same namespace is the same thing.  Which is where EA is wrong.

I will reiterate what he said, UML does not require multiple renditions of the same classifier in a diagram as a compliance requirement.  However, neither does it require single renditioning (?) as a compliance requirement.

But it does say, an element in a model with the same name in the same namespace IS the same thing.

When this thread started, people were discussing why or why not you cannot have the same thing more than once in a diagram in EA.  I am trying to show that you can, but there is fundamental short-falling within EA as to what constitutes "the same thing".  

In short UML is agreeably (or if you will, disagreeably) silent, but EA is wrong.

capiche?

bruce

(Please don't take this the wrong way. I am not shouting.  However, IMO it should have been addressed some time ago.  Clarity in modeling is the objective.)