Author Topic: Multiple instances of element in diagram  (Read 29288 times)

Jan Vlcinsky

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Multiple instances of element in diagram
« on: February 05, 2009, 11:52:59 pm »
Trying to place the same element second time in diagram results currently (EA 7.1) in alert box telling

This diagram already contains an instance of the element you are trying to paste.
Currently, only one instance is supported, so you cannot paste the element here.

I have read annoncement about EA 7.5 beta and wonder, if the possibility for multiple instances in one diagram is going to be here. I did not find there any note about this.

Reasoning: For diagrams with bigger number of elements and more relations one gets into problem, that some relationships would have to cross half of others and result becomes quite cluttered. UML allows to insert another instance of the element (e.g. class) and link related relationships there.
 When discussing EA functionality with other power users, they very often mention this problem even without having to name the problem and asking for severity of it.

Eve

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Re: Multiple instances of element in diagram
« Reply #1 on: February 06, 2009, 08:16:48 am »
No, it's not in 7.5.

Frank Horn

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Re: Multiple instances of element in diagram
« Reply #2 on: February 06, 2009, 06:21:54 pm »
And if you ever include it, please make it optional so I can configure EA to work the old way.

I guess I'd use it while documenting the dependencies of legacy code, but it would mean a lot of work. You would have to set the individual visibility of all connectors (and EA would have to save it per diagram and per instance) to make a diagram readable.

For planning and designing purposes I'd rather have a warning when I inadvertently drop an element a second time. And if a diagram gets so complicated I would need second instances, I'd rather stop it, have a cup of coffee, and think up a better structure.

seanassurant

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Re: Multiple instances of element in diagram
« Reply #3 on: February 19, 2009, 07:07:49 am »
Add me to the want list. Even choosing a diagram like Extended->Analysis, which has no restrictions or standards gets you nowhere. So if you have to put together a business, or executive level presentation about business processes you either need to hack up your model with a folder full of 'dupes' or head off to Visio.

Oliver F.

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Re: Multiple instances of element in diagram
« Reply #4 on: February 19, 2009, 11:30:11 pm »
Quote
Add me to the want list. Even choosing a diagram like Extended->Analysis, which has no restrictions or standards gets you nowhere. So if you have to put together a business, or executive level presentation about business processes you either need to hack up your model with a folder full of 'dupes' or head off to Visio.

Be aware that having multiple objects in one diagram breaks the idea behind most UML diagrams. In the systems modeled there is always only one type of an element and everything else is an instance of that type.

Imagine having a complex activity diagram where the same activity is present in multiple branches which would require that both share the same connections. That would make the diagram totally unreadable. If I added a new connector to one it would surely be valid for the second also.
A class is a unique element type as well as a component and a use case is.
If you want to show the same element in several different aspects it is best practice to show this in a separate view (aka diagram) and do a nested/composite model structure. This also applies to business processes and requirements- not only technical UML models.

Oliver

bioform

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Re: Multiple instances of element in diagram
« Reply #5 on: February 20, 2009, 01:28:07 am »
Exactly.... If you are creating diagrams that big... then you really need to consider the use of composite features to hide detail or to break the activity into smaller logical parts.

I think you can say that "feature" will not be available until the UML specification would change, and as Oliver states that really would lead to multiple problems... Smaller, Simpler, Clearer... Go team!

David
Time is what keeps everything from happening at once, Space is what keeps it all from happening to you. <unknown>

seanassurant

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Re: Multiple instances of element in diagram
« Reply #6 on: February 20, 2009, 02:45:46 am »
Quote
Quote
Add me to the want list. Even choosing a diagram like Extended->Analysis, which has no restrictions or standards gets you nowhere. So if you have to put together a business, or executive level presentation about business processes you either need to hack up your model with a folder full of 'dupes' or head off to Visio.

Be aware that having multiple objects in one diagram breaks the idea behind most UML diagrams. In the systems modeled there is always only one type of an element and everything else is an instance of that type.

Imagine having a complex activity diagram where the same activity is present in multiple branches which would require that both share the same connections. That would make the diagram totally unreadable. If I added a new connector to one it would surely be valid for the second also.
A class is a unique element type as well as a component and a use case is.
If you want to show the same element in several different aspects it is best practice to show this in a separate view (aka diagram) and do a nested/composite model structure. This also applies to business processes and requirements- not only technical UML models.

Oliver

Then remove the non-UML model types from EA. I'm talking about flowcharts, and analysis diagrams where you just need to get your artifacts on a diagram to help present a picture of your enterprise to a bunch of executives.

"Analysis Diagrams are simplified Activity diagrams used to describe high-level business processes with less UML formality."

That description (by Sparx) is false, the "Analysis" diagram is held to standards. High-level business process to me means something like "Pay Claim", or even "Claims Processing". If I want to create a diagram showing a landscape of applications (as clouds, borders, or whatever) and I want to show the business process inside them (rather then having lines all over which would imply that they all use the same business processing 'service') I can't. A DFD is another example of a diagram that has no such limitation (or real standards).

Oliver F.

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Re: Multiple instances of element in diagram
« Reply #7 on: February 20, 2009, 07:20:58 pm »
Quote
Then remove the non-UML model types from EA. I'm talking about flowcharts, and analysis diagrams where you just need to get your artifacts on a diagram to help present a picture of your enterprise to a bunch of executives.

Sean, I accept your motivation and see your issue. However the problems of duplicate elements will remain, especially when it comes to connecting elements together, changing appearance, creating references or searching in diagrams. This is regardless the type of elements or diagrams you are creating and I assume that the efforts of implementing a clean solution (touching various aspects in the model and diagram handling) which is satisfactory for most application are rather high not justifying the cause.

Oliver

seanassurant

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Re: Multiple instances of element in diagram
« Reply #8 on: February 21, 2009, 02:14:52 am »
Quote
Quote
Then remove the non-UML model types from EA. I'm talking about flowcharts, and analysis diagrams where you just need to get your artifacts on a diagram to help present a picture of your enterprise to a bunch of executives.

Sean, I accept your motivation and see your issue. However the problems of duplicate elements will remain, especially when it comes to connecting elements together, changing appearance, creating references or searching in diagrams. This is regardless the type of elements or diagrams you are creating and I assume that the efforts of implementing a clean solution (touching various aspects in the model and diagram handling) which is satisfactory for most application are rather high not justifying the cause.

Oliver

No arguments here, it's a modeling tool not a presentation tool. However as you climb the chain in an organization eventually you need presentations that even numb minded executives with marketing degrees can 'understand'. Visio it is for now.

Thelonius

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Re: Multiple instances of element in diagram
« Reply #9 on: February 22, 2009, 12:36:54 pm »
Quote
Quote
Quote
Then remove the non-UML model types from EA. I'm talking about flowcharts, and analysis diagrams where you just need to get your artifacts on a diagram to help present a picture of your enterprise to a bunch of executives.

Sean, I accept your motivation and see your issue. However the problems of duplicate elements will remain, especially when it comes to connecting elements together, changing appearance, creating references or searching in diagrams. This is regardless the type of elements or diagrams you are creating and I assume that the efforts of implementing a clean solution (touching various aspects in the model and diagram handling) which is satisfactory for most application are rather high not justifying the cause.

Oliver

No arguments here, it's a modeling tool not a presentation tool. However as you climb the chain in an organization eventually you need presentations that even numb minded executives with marketing degrees can 'understand'. Visio it is for now.

What if the 'duplicate' was merely a 'ghost' image - not a real component / element - just a replicant that referred back to the single 'real' element?

Even connections from other elements to the 'ghost replicant' would - in terms of the UML model and repository - show up as being connected to the one single 'real' element?

Thinking laterally here ... we need to preserve the integrity of UML - but it would be nice to be able to create simpler presentation material for 'numb minded executives'  ;)

Oliver F.

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Re: Multiple instances of element in diagram
« Reply #10 on: February 23, 2009, 08:25:36 pm »
Quote

What if the 'duplicate' was merely a 'ghost' image - not a real component / element - just a replicant that referred back to the single 'real' element?

How would that be different to the (exisiting) "instance of" type?  ;)

Oliver

Thelonius

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Re: Multiple instances of element in diagram
« Reply #11 on: February 23, 2009, 08:36:55 pm »
Quote
Quote

What if the 'duplicate' was merely a 'ghost' image - not a real component / element - just a replicant that referred back to the single 'real' element?

How would that be different to the (exisiting) "instance of" type?  ;)

Oliver

Not sure, Oliver. But let me use an example to find out what you're referring to.

So if I have a 'Component' element in a busy, large, complex diagram, and it would be really useful to have a copy of the same element on the same diagram just for presentation purposes - with connectors from the copy to certain other components - how can I create an 'instance of' one of the Components and have both on the same diagram?

Or does my question belie my lack of understanding of the nuances of UML?
 :-[

Oliver F.

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Re: Multiple instances of element in diagram
« Reply #12 on: February 23, 2009, 11:23:44 pm »
Quote
Quote
Quote

What if the 'duplicate' was merely a 'ghost' image - not a real component / element - just a replicant that referred back to the single 'real' element?

How would that be different to the (exisiting) "instance of" type?  ;)

Oliver

Not sure, Oliver. But let me use an example to find out what you're referring to.

So if I have a 'Component' element in a busy, large, complex diagram, and it would be really useful to have a copy of the same element on the same diagram just for presentation purposes - with connectors from the copy to certain other components - how can I create an 'instance of' one of the Components and have both on the same diagram?

In default configuration you get a dialog to choose whether to drag the element as a link (which you normally do), an instance or a new element. If you have diabled this dialog you can enforce it by dragging and dropping  the element from the project browser while holding the Ctrl-Key.

Quote
Or does my question belie my lack of understanding of the nuances of UML?
 :-[

Not at all.
My proposal was more of some sort of workaround. The "ghost" element you described behaved like an instance- it has the same type but different connectors.
But in fact its meaning in UML is different as the "ghost" element and I believed that it would be valid to be used for business process descriptions as there is no "instance of".
However I would not apply this method to class, component, use case and other UML diagrams because it invalids their meaning and intention.

Oliver

Geert Bellekens

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Re: Multiple instances of element in diagram
« Reply #13 on: March 04, 2009, 05:59:39 pm »
Me too!
This is one of the biggest drawbacks I see in EA with regards to other modelling tools.
And for those opposed: nowhere int he UML specs it says that you cannot represent a certain element twice on a diagram. In a lot of cases it would make life a lot easier if we could just add an element more then once on a diagram. It allows to draw a much cleaner diagram without connectors that have to go all over the place.
As an example consider a usecase diagram with say 5 actors and 5 usecases. Now try to make a clean diagram when each actor needs to be connected to at least three (random) usecases.
If we could add the representation of the actor twice on the diagram that would be very easy.
There is in my mind no danger to that. A diagram is just a specific view on the model. It's not because on one representation you only show three links, and on another you show three other links that the actual element in the model doesn't have all six links.
I do believe that it won't be an easy change for the guys from Sparx, since this one-to-one relation between element and diagram is probably hardcoded pretty deep in the application logic (and database)

skiwi

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Re: Multiple instances of element in diagram
« Reply #14 on: August 29, 2012, 10:34:28 am »
bump
Orthogonality rules
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