How to show constraints?

[dserodio]

I can add a constraint to a class thru a class' properties dialog, on the "Constraints" tab.
Constraints added this way don't appear on the diagram.

I can also add a constraint to a class by right-clicking it and choosing "Attach / Attach Constraint". But constraints added this way don't appear on the class' properties.

Why are there two kinds of constraints? What is the difference between them?

Thanks.

[thomaskilian]

You can show class constraints in the diagram: Select diagram properties; check "Show constraints".

[dserodio]

Thanks, but I still don't understand the difference between these two types of constraints.

[thomaskilian]

Hmm. Hard to tell. There are similar differences in requirement, to do's, issues a.s.o. The attached note gives you a relation and some separate element whilst the class constraint is mor like a property. I also would like to have all of these more straightforeward than this double action  :-/

[dserodio]

I think they should all be (classes', in this example) properties. Should I file a bug report against this?

Are you (Thomas) an EA employee, or an EA user?

[sargasso]

The difference between innies and outies!

In general all constraints on a class should be created and managed within the class properties.

However, there are times when a constraint applies to the context for which the diagram was created and is not a constraint to be applied to the class in general.  I cant think of a salient generalised example here, you'll have to use your imagination.

Secondly, there are instances where a constraint does not apply to a single class but exists as a constraint on a structure created by the co-existence of two or more classes on the same diagram - simple example being mutual exclusivity (a "co-singleton"??).

Ergo "outey" constraints do have their places.

hth
bruce

[dserodio]

I see. Thanks for the clarification. Maybe your explanation should be in EA's docs?  

[thomaskilian]

Hi dserodio,
I'm just a user like you. Sparx stuff can be recognized at the 5 red stars. Regarding the documentation: it's already a 1000 pages. Surely you would not have found the explanation if it was inside Most times it's easier to ask the forum.

[dserodio]

Can constraints created and managed within the class properties be shown on the diagram as a "Note", instead of in a compartment in the class?.

[sargasso]

Yes they can and I reckon this is one of the best things I have seen in EA.

Just create a blank note in the diagram and link it to the class using a note link.  Then right click on the note link, you will see a menu item Link This Note to an Element Feature...

Explore - enjoy.

bruce

[KP]

Can constraints created and managed within the class properties be shown on the diagram as a "Note", instead of in a compartment in the class?

Yes. Add a note to your diagram then draw a note link from note to class. Right-click the note link and select "Link this note to an element feature". For Feature Type choose "Constraint" and choose the constraint you want to display from the list.

UPDATE: Bruce has beaten me to it and somebody has already posted the same answer in a different thread. Oh well...  

[dserodio]

Great! Thanks for the tip. I don't mean to be picky, but shouldn't this note have a "invariant", "pre-condition", etc stereotype? I think it would communicate better.