Eclipse Community Forums: UML2 Tools » Associations: Are they good for anything?

Help

Home

Home » Modeling » UML2 Tools » Associations: Are they good for anything?

Show: Today's Messages :: Show Polls :: Message Navigator

Associations: Are they good for anything? [message #473256]

Wed, 30 January 2008 20:22

Eclipse User

Originally posted by: m_lehmeier.gmx.de

Situation:
I read the "Using EMF" Tutorial at
http://www.eclipse.org/articles/Article-Using%20EMF/using-em f.html

It showed an UML diagram that is used to build the example metamodel.
It was done in Rational Rose, but I thought there are the uml2tools,
they should also be able to do that.

So I created a diagram and basically copied that diagram.
I didn't find out how to put the arrows on the associations, but I guess
that is not so important.

Note:
That important stuff like multiplicities have to be manually edited in
the properties and are even distributed into no less than four property
fields is very nasty and time-consuming. I hope this will be changed
soon.

Anyway, I then generated an EMF model out of the result which went fine.
The resulting model however, showed no associations. No reference
fields.

I wonder: Isn't model generation the main task of the uml2tools? If yes,
then it seems that associations only serve for decoration in the
diagram.
I hope not.

I wonder this especially because in the tutorial
http://www.vogella.de/articles/UML/article.html
the chapter for the explanation of associations makes up a pretty big
part.
But it never explains what purpose they serve in modeling with
uml2tools.
Or how to edit the multiplcities for that matter.

My suggestion to whoever made the tutorial is to add one example how all
the editing reflects in a concrete result, meaning either a generated
model, generated java code or whatever.

--
Lehmeier Michael (Nightshade Dragon UDIC)

8:00 - 12:00 : Frohlocken!
12:00 - 20:00 : Hosianna singen!

Report message to a moderator

Re: Associations: Are they good for anything? [message #473259 is a reply to message #473256]

Thu, 31 January 2008 14:49

Felix Dorner

Messages: 676
Registered: July 2009

Senior Member

Hi Michael,

Michael Lehmeier wrote:
> It showed an UML diagram that is used to build the example metamodel.
> It was done in Rational Rose, but I thought there are the uml2tools,
> they should also be able to do that.

First you should understand that UML2Tools generates UML2 Models. You
can export these models to Ecore just like you describe below (I suppose
you used the UMl2Ecore model exporter?). To directly create Ecore
model(s) (diagrams) you could use the EMFT Diagram editor, or the
praised Topcase editor. (Maybe these are actually the same now?)

> So I created a diagram and basically copied that diagram.
> I didn't find out how to put the arrows on the associations, but I guess
> that is not so important.

Did you consider reading an introductory UML Book? They recommended UML
Glasklar to me (in German). This should definitely explain how
associations work.

> That important stuff like multiplicities have to be manually edited in
> the properties and are even distributed into no less than four property
> fields is very nasty and time-consuming. I hope this will be changed
> soon.

I maybe agree. One could have one property field to enter upper and
lower multiplicity at a Time, like 0..* or so. The current
implementation just generically has a property field for every property
of the selected UML element. All commercial tools that I´ve seen so far
also use the 4 property fields approach too...

> Anyway, I then generated an EMF model out of the result which went fine.
> The resulting model however, showed no associations. No reference
> fields.

How did you actually look at this model? The EMF Tree Editor? Maybe you
could post your original UML2 Model? This is actually not really an
UML2Tools Issue, but more an UML2 or Ecore question, you might consider
posting a seperate question on the UML2 or Ecore Group.

> I wonder: Isn't model generation the main task of the uml2tools? If yes,
> then it seems that associations only serve for decoration in the
> diagram.
> I hope not.

No need to pray here... UML2 Tools merely creates UML2 Models by using
the notation we all know (or don´t no so well, it has a lot of
pitfalls...). It does so by relying on the UML2 Project which basically
provides an API to create UML2 models (look at the .uml2 file with a
Text Editor, this is equivalent to your diagram)

After you created your UML2 model, it´s up to you what you want do with
it. E.g. UML2 does not provide a code generation framework. Therefore
they created the UML2 to Ecore exporter, since Ecore generates first
class vanilla strawberry tastin´ code from your models. However some
things are not supported by that exporter - due to the fact that UML is
somehow more powerful (also much more complex) than Ecore.

> But it never explains what purpose they serve in modeling with
> uml2tools.

You cannot just read Vogellas Tutorial and understand UML from his
Examples. You definitely should read a book on the issue. I also
recommend to look at Ecore directly, they are releasing a very promising
new Book in a few years :-p (maybe a few weeks...)

Felix

Report message to a moderator

Re: Associations: Are they good for anything? [message #473262 is a reply to message #473259]

Fri, 01 February 2008 01:28

Eclipse User

Originally posted by: m_lehmeier.gmx.de

On 2008-01-31, Felix Dorner <felix_do@web.de> wrote:
> Hi Michael,
>
>
> Michael Lehmeier wrote:
>> It showed an UML diagram that is used to build the example metamodel.
>> It was done in Rational Rose, but I thought there are the uml2tools,
>> they should also be able to do that.
>
> First you should understand that UML2Tools generates UML2 Models. You
> can export these models to Ecore just like you describe below (I suppose
> you used the UMl2Ecore model exporter?).

File->New->EMF-Model
Then select "UML Model" when asked from what it should be created.

> To directly create Ecore
> model(s) (diagrams) you could use the EMFT Diagram editor, or the
> praised Topcase editor. (Maybe these are actually the same now?)

I didn't know there was a graphical tool for EMF modeling.
Good to know.
But I didn't need it yet anyway.

>> So I created a diagram and basically copied that diagram.
>> I didn't find out how to put the arrows on the associations, but I guess
>> that is not so important.
>
> Did you consider reading an introductory UML Book? They recommended UML
> Glasklar to me (in German). This should definitely explain how
> associations work.

Indeed I have a book here (The one from Booch, Rumbeaugh, Jacobson) and
have read it.
Oh, you mean the arrows not important? Of course they are important,
just not in the case that I was using them for here. I should have made
that more clear.
Anyway, I still haven't found out how to make an association navigable
(in one direction) in uml2tools.

>> That important stuff like multiplicities have to be manually edited in
>> the properties and are even distributed into no less than four property
>> fields is very nasty and time-consuming. I hope this will be changed
>> soon.
>
> I maybe agree. One could have one property field to enter upper and
> lower multiplicity at a Time, like 0..* or so. The current
> implementation just generically has a property field for every property
> of the selected UML element. All commercial tools that I´ve seen so far
> also use the 4 property fields approach too...

I think the problem is that uml2tools share the same properties editor
with all other Eclipse plugins. It is not very optimized for UML
editing. Tools like ArgoUML are so much easier there.

> This is actually not really an
> UML2Tools Issue, but more an UML2 or Ecore question, you might consider
> posting a seperate question on the UML2 or Ecore Group.

Yes, I see that now.
I will probably ask there when I have the time.

>> I wonder: Isn't model generation the main task of the uml2tools? If yes,
>> then it seems that associations only serve for decoration in the
>> diagram.
>> I hope not.
>
> After you created your UML2 model, it´s up to you what you want do with
> it. E.g. UML2 does not provide a code generation framework. Therefore
> they created the UML2 to Ecore exporter, since Ecore generates first
> class vanilla strawberry tastin´ code from your models. However some
> things are not supported by that exporter - due to the fact that UML is
> somehow more powerful (also much more complex) than Ecore.

I just thought that associations are the logical UML representation of
Ecore references. How else could I model references with the UML tool?
I understand that not every feature of UML maps to something in Ecore,
but considering how powerful UML is, there should be *some* way to model
Ecore references with UML.

BTW, the example model from that tutorial was created with Rational
Rose. There was the Rational Rose Model of that diagram as a file, which
I could use for import to Ecore, with references and everything.
Since I don't have Rational Rose, I can't test if there was more to the
file than what I saw in the diagram, but because of that example I just
assumed that the UML generated from UML2Tools should also be able to map
associations to ecore references.

Apparently not.

>> But it never explains what purpose they serve in modeling with
>> uml2tools.
>
> You cannot just read Vogellas Tutorial and understand UML from his
> Examples. You definitely should read a book on the issue.

Of course, but the tutorial spends quite some time explaining
associations like talking to an absolute beginner.
But an absolute beginner usually also requires an example what to
actually do with it, or he will look for something else..

I mean, if I want to "sell" Uml2Tools to a beginner, if asking "what
do I get from an UML diagram?" you shouldn't answer "an UML2 model", because
immediate next question would be "and what do I do with an UML2 model?".

And someone who already knows what to do with the UML2 model surely
needn't be told what the difference between a aggregation and a
composition is, because he already knows that.

I just think that the tutorial really needs an example for a practical
application of the results.
Much more than an introduction to UML, that makes up about a third of
the whole tutorial!

> I also
> recommend to look at Ecore directly,

Where's the fun in that?
Until now I modeled ecore in plain-text KM3. I thought UML should also
do it since it can be importet to Ecore. I failed, so I am back to KM3.

I don't need Uml2Tools, I just hoped it would help me.
I will have a look at EMFT though.

--
Lehmeier Michael (Nightshade Dragon UDIC)

8:00 - 12:00 : Frohlocken!
12:00 - 20:00 : Hosianna singen!

Report message to a moderator

Re: Associations: Are they good for anything? [message #473265 is a reply to message #473262]

Fri, 01 February 2008 10:28

Felix Dorner

Messages: 676
Registered: July 2009

Senior Member

Hi Michael,

Michael Lehmeier wrote:
> I didn't know there was a graphical tool for EMF modeling.
> Good to know.
> But I didn't need it yet anyway.

I don't understand you. You created an UML model to then export it to
EMF. Why not directly edit Ecore models with the EMFT Editor and fall
into traps like the UML2Ecore mapping. This doesn't mean that you cannot
rely on this mapping, it worked fine in my simple test cases. For your
case, it would really be good to get a look at your UML source model, to
check why the eReferences are not created. (Maybe association ends were
owned by the association?)

> Anyway, I still haven't found out how to make an association navigable
> (in one direction) in uml2tools.
In the tool-panel, click on the small black triangle. This opens sort of
combobox with an element "Navigable Association". Select this and draw
your associacion from the src to the target class.

> Tools like ArgoUML are so much easier there.
That's a statement. I considered ArgoUML crap after 3 minutes :-p I am
curious: How do you enter multiplicities with that tool?

> I just thought that associations are the logical UML representation of
> Ecore references.
Hmm. UML associations are UML associations. These are similar to Ecore
references i.e. represent similar concepts, but they are not the same,
since you use a different (yet similar) language...

> I just
> assumed that the UML generated from UML2Tools should also be able to map
> associations to ecore references.
It definitely is.

> I just think that the tutorial really needs an example for a practical
> application of the results.
> Much more than an introduction to UML, that makes up about a third of
> the whole tutorial!

People are always invited to contribute.

>> I also
>> recommend to look at Ecore directly,
>
> Where's the fun in that?
> Until now I modeled ecore in plain-text KM3. I thought UML should also
> do it since it can be importet to Ecore. I failed, so I am back to KM3.

The Fun in that is that you have no pain from modeling in a different
language and hope that the mapping works as you intend to. From your
statments it looks like you already "Think Ecore" when you are acutally
model UML... I don't think that's what the mapping was designed for.

Felix

Report message to a moderator

Re: Associations: Are they good for anything? [message #473271 is a reply to message #473265]

Fri, 01 February 2008 12:47

Ed Merks

Messages: 33137
Registered: July 2009

Senior Member

This is a multi-part message in MIME format.
--------------030204080509090902050807
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

Felix,

Comments below.

Felix Dorner wrote:
> Hi Michael,
>
> Michael Lehmeier wrote:
>> I didn't know there was a graphical tool for EMF modeling.
>> Good to know.
>> But I didn't need it yet anyway.
>
> I don't understand you. You created an UML model to then export it to
> EMF. Why not directly edit Ecore models with the EMFT Editor and fall
> into traps like the UML2Ecore mapping. This doesn't mean that you
> cannot rely on this mapping, it worked fine in my simple test cases.
> For your case, it would really be good to get a look at your UML
> source model, to check why the eReferences are not created. (Maybe
> association ends were owned by the association?)
Yes, I didn't quite understand not wanting to edit Ecore graphically
directly either and I had the same though about owned association ends.
This recent blog seems relevant to the topic of what happens with
associations that own their ends:

http://ed-merks.blogspot.com/2008/01/modeling-associations-w ith-ecore.html

>
>> Anyway, I still haven't found out how to make an association navigable
>> (in one direction) in uml2tools.
> In the tool-panel, click on the small black triangle. This opens sort
> of combobox with an element "Navigable Association". Select this and
> draw your associacion from the src to the target class.
>
>> Tools like ArgoUML are so much easier there.
> That's a statement. I considered ArgoUML crap after 3 minutes :-p I am
> curious: How do you enter multiplicities with that tool?
Why don't you say how you really feel? :-P
>
>> I just thought that associations are the logical UML representation of
>> Ecore references.
> Hmm. UML associations are UML associations. These are similar to Ecore
> references i.e. represent similar concepts, but they are not the same,
> since you use a different (yet similar) language...
>
>> I just
>> assumed that the UML generated from UML2Tools should also be able to map
>> associations to ecore references.
> It definitely is.
>
>> I just think that the tutorial really needs an example for a practical
>> application of the results.
>> Much more than an introduction to UML, that makes up about a third of
>> the whole tutorial!
>
> People are always invited to contribute.
>
>>> I also
>>> recommend to look at Ecore directly,
>>
>> Where's the fun in that?
>> Until now I modeled ecore in plain-text KM3. I thought UML should also
>> do it since it can be importet to Ecore. I failed, so I am back to KM3.
>
> The Fun in that is that you have no pain from modeling in a different
> language and hope that the mapping works as you intend to. From your
> statments it looks like you already "Think Ecore" when you are
> acutally model UML... I don't think that's what the mapping was
> designed for.
>
> Felix
>
>

--------------030204080509090902050807
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type">
</head>
<body bgcolor="#ffffff" text="#000000">
Felix, 
 
Comments below. 
 
 
Felix Dorner wrote:
<blockquote cite="mid:fnus8m$cu7$1@build.eclipse.org" type="cite">Hi
Michael,
 
 
Michael Lehmeier wrote:
 
<blockquote type="cite">I didn't know there was a graphical tool for
EMF modeling.
 
Good to know.
 
But I didn't need it yet anyway.
 
</blockquote>
 
I don't understand you. You created an UML model to then export it to
EMF. Why not directly edit Ecore models with the EMFT Editor and fall
into traps like the UML2Ecore mapping. This doesn't mean that you
cannot rely on this mapping, it worked fine in my simple test cases.
For your case, it would really be good to get a look at your UML source
model, to check why the eReferences are not created. (Maybe association
ends were owned by the association?)
 
</blockquote>
Yes, I didn't quite understand not wanting to edit Ecore graphically
directly either and I had the same though about owned association
ends.  This recent blog seems relevant to the topic of what happens
with associations that own their ends: 
<blockquote><a
href=" http://ed-merks.blogspot.com/2008/01/modeling-associations-w ith-ecore.html"> http://ed-merks.blogspot.com/2008/01/modeling-associations-w ith-ecore.html</a> 
</blockquote>
<blockquote cite="mid:fnus8m$cu7$1@build.eclipse.org" type="cite"> 
<blockquote type="cite">Anyway, I still haven't found out how to make
an association navigable
 
(in one direction) in uml2tools.
 
</blockquote>
In the tool-panel, click on the small black triangle. This opens sort
of combobox with an element "Navigable Association". Select this and
draw your associacion from the src to the target class.
 
 
<blockquote type="cite"> Tools like ArgoUML are so much easier there.
 
</blockquote>
That's a statement. I considered ArgoUML crap after 3 minutes :-p I am
curious: How do you enter multiplicities with that tool?
 
</blockquote>
Why don't you say how you really feel?  :-P 
<blockquote cite="mid:fnus8m$cu7$1@build.eclipse.org" type="cite"> 
<blockquote type="cite">I just thought that associations are the
logical UML representation of
 
Ecore references. </blockquote>
Hmm. UML associations are UML associations. These are similar to Ecore
references i.e. represent similar concepts, but they are not the same,
since you use a different (yet similar) language...
 
 
<blockquote type="cite">I just
 
assumed that the UML generated from UML2Tools should also be able to
map
 
associations to ecore references.
 
</blockquote>
It definitely is.
 
 
<blockquote type="cite">I just think that the tutorial really needs
an example for a practical
 
application of the results.
 
Much more than an introduction to UML, that makes up about a third of
 
the whole tutorial!
 
</blockquote>
 
People are always invited to contribute.
 
 
<blockquote type="cite">
<blockquote type="cite">I also
 
recommend to look at Ecore directly, </blockquote>
 
Where's the fun in that?
 
Until now I modeled ecore in plain-text KM3. I thought UML should also
 
do it since it can be importet to Ecore. I failed, so I am back to KM3.
 
</blockquote>
 
The Fun in that is that you have no pain from modeling in a different
language and hope that the mapping works as you intend to. From your
statments it looks like you already "Think Ecore" when you are acutally
model UML... I don't think that's what the mapping was designed for.
 
 
Felix
 
 
 
</blockquote>
 
</body>
</html>

--------------030204080509090902050807--

Ed Merks
Professional Support: https://www.macromodeling.com/

Report message to a moderator

Re: Associations: Are they good for anything? [message #473289 is a reply to message #473271]

Fri, 01 February 2008 14:22

Felix Dorner

Messages: 676
Registered: July 2009

Senior Member

Hey Ed,

> Yes, I didn't quite understand not wanting to edit Ecore graphically
> directly either and I had the same though about owned association ends.
> This recent blog seems relevant to the topic of what happens with
> associations that own their ends:
>
> http://ed-merks.blogspot.com/2008/01/modeling-associations-w ith-ecore.html
>
>

I had read your article a week or so ago, It comes to the right time as
my thesis topic deals with object relationships and their support in OO
Pl's. I am still looking forward to post some comments at your site.

Felix

Report message to a moderator