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According to the UML 2.5 specification, an association end can be "owned" by the class at the other end (this means that the owned association end corresponds to a reference property of the class at the other end). The fact that an association end is owned should not be expressed by a navigability arrow (which is common practice, however). Rather, it has to be expressed with the help of a small filled circle (also called a "dot") at the end of the association line, as the following diagram illustrates.

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Is there a free class diagram editor that supports these ownership dots? For instance, Visio 2010 does not support it.

Gerd Wagner
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  • Do you really need it? It is a very ancient option, Using simply an arrow you are showing THE SAME THING. Nobody *normally* realizes the two-ended association as a class. Using the point in the VP UML changes absolutely nothing in the code generated. 90% of materials on this theme obviously are copying one form another and understand nothing in the subject, the left 10% explain it the same way as the arrow end. – Gangnus Jan 24 '14 at 09:08
  • As for a free editor, it seems to me, that Papyrus is very elaborated and should have it, but I can check it at home only - in 12 hour you'll know it precisely. – Gangnus Jan 24 '14 at 09:12
  • The UML 2.5 specification explicitly states that the use of navigability arrows for expressing _association end ownership_ (corresponding to a reference property) is **depreciated**. I think that the current UML tools are not yet up-to-date with respect to UML 2.5. – Gerd Wagner Jan 24 '14 at 09:29
  • Maybe. Than I would like to find a source that can explain what it is. And on standard pages UML ends with 2.4.1. 2.5 is UML simplified - something strange. If you go to the page, you can see it is BETA version. The last ISO adopted specification is 2.4.1. – Gangnus Jan 24 '14 at 10:08
  • Just read the new UML 2.5 spec. It is very clear about this point. Navigability was never well-defined ("Navigability means instances participating in links at runtime (instances of an association) can be accessed efficiently from instances participating in links at the other ends of the association. The precise mechanism by which such access is achieved is implementation specific. If an end is not navigable, access from the other ends may or may not be possible"). Therefore, the new UML 2.5 definition of visualizing association end ownership is an important disambiguation. – Gerd Wagner Jan 24 '14 at 10:27
  • According to http://searchsoa.techtarget.com/feature/Steve-Cook-on-what-architects-can-expect-from-UML-25-revision, the 2.5 doesn't change things, but merely simplifies the documentation. (as for me, not too much) – Gangnus Jan 24 '14 at 10:53
  • You didn't get the point: the "arrow" denotes navigability, and navigability does not mean ownership of the association end! It was just used in this way by many UML users because the UML spec was unclear on this point. But now they clarified this and we should gratefully use the new dot notation. – Gerd Wagner Jan 24 '14 at 10:54
  • Thank you. After reading your last comment and chapters 9 and 11 of 2.5 standard I finally understood WHAT they meant. Arrow means that you can reach other class instance, and point means you have it. "Navigability means that instances participating in links at runtime (instances of an Association) can be accessed efficiently from instances at the other ends of the Association. The precise mechanism by which such efficient access is achieved is implementation specific." – Gangnus Jan 24 '14 at 12:52
  • But then, according to 2.5, BOTH ends are usable, not the point only. – Gangnus Jan 24 '14 at 12:55
  • +1 and thank you for the explanation. But better notice in the question, that navigability, where you don't set the ownership, is still a good old arrow. – Gangnus Jan 24 '14 at 13:02

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Yes, I have checked the Papyrus diagram editor. It has properties for association and you can choose, if an end belongs to association or classifier. And shows the dot or both of them.

You need to install Eclipse for it. You can choose Eclipse for modelling, or take ANY Eclipse and later go to Help>Install New Software, input 'Kepler - http://download.eclipse.org/releases/kepler' to Work In, type 'papyrus' into filter text, choose the Papyrus and later agree with everything. It is not Release version, but it is a good Beta. Papyrus is NOT worse than the most renown proprietary tools, as EA or VP and is far better than IBM Modeller.

Gangnus
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