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Please I need help in understanding this two approaches in the uml world. I am a programmer who is new to uml. I just started learning uml lately but kept getting this phrase asked all the time. - Are you modelling or drawing?. An explanation is needed with clear examples. This link hinted just a little but I am stil confused -- http://modeling-languages.com/drawing-tools-vs-modeling-tools/

Christophe
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Emeka Obianom
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2 Answers2

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UML is a modeling language, which has a graphical notation. Its semantic is precisely specified by UML 2.5 standard of the OMG and also the international standards ISO 19505-1:2012 and 19505-2:2012 (although the latter corresponds to UML 2.4.1).

THere are two different approaches to UML diagramming. And it's heavily influenced by the tools you use:

  • Drawing tools generally offer UML shapes to be used in drawings. But there is no deeper meaning behind the shapes. It's only pictures. These tools would allow you to mix a use case with a class or an actor in a deployment diagram. The advantage is that you can do what you want. The inconvenience is that what you want may not be compliant.

  • Real modeling tools let you combine only valid UML elements together and ensure consistency of what you draw with the deeper meaning of the UML language. And they build a true and comprehensive model behind the scene by combining all the facets of the different diagrams.

Modeling tools can do smarter things. They can relate for example a class to their object instantiations in sequence diagram. They can help you to find all the other models in which a specific class is used. If you rename a class or add a property in one diagram, it'll be automatically reflected in all the others.

Modeling requires more discipline, but it's more powerful in the end. Some modelling tools can even use their understanding of UML to generate code out of the model.

Christophe
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    I really support this one. Sounds more meaningful to me. – Emeka Obianom Jun 24 '17 at 18:50
  • Haven't you simply repeated my answer? – Gangnus Jun 26 '17 at 09:24
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    @Gangnus our answer may have some common aspects, but I don't think that I repeat yours. First, I don't think that "the use of uml is not predefined". I think on contrary that if uml is used, the standard should be respected. This is why I start reminding that uml is a well defined language. Beyond the description of drawing and modelling which we both address, although with different examples and a slightly different viewpoint, I also develop the benefits of modelling, i.e outside the area of visual aspects of diagramming. And that is in my view the real difference btw them – Christophe Jun 26 '17 at 11:59
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    Actually, UML _does_ allow to mix (almost) anything in any diagram. But for good reason there is a classification of diagrams defined in UML also. So the mix is thought as exception. But it's not forbidden. – qwerty_so Oct 08 '21 at 21:00
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You can use UML diagrams in very free way and you can use them up to the specifications. There are even different UML tools - some support only free style diagrams/drafts, some check dependencies and correctness and thus create models. There are some tools in between (MS Visio is one of them)

Nothing is ideal and fitting for everything. For example, some strict tools (VP and EA) forbid to make number-named classes, but according to UML specification you MUST use number names for anonymous classes. But -sigh- we have what we have.

Use of UML as such is not strictly predefined. So, you can use it for freehand drafts, later work on them more thoroughly and make them models. Or do only drafts. Or only models. But at any moment you should know how strictly are you keeping up to specifications. Or at least, trying to keep up. But even very free draft can help you greatly to understand the task or to think in a more productive way.

Gangnus
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