Derived attributes in BUML

[ademait]

Is your feature request related to a problem?

There is no way to set derived, calculated attributes.

Describe the solution you'd like

We could use the notation used in UML for derived attributes (slash before the name), and then use an annotation to set the way it is calculated. In the Web Modeling Editor we could use the same boxes are used for OCL (if possible, since there is also the "check OCL" functionality).

Describe alternatives you've considered

For now, what I have done is use OCL to set a restriction to the derive attribute. For instance, if we have a Product class with two attributes for price, one without tax and another with tax, and an attribute for tax, I write:

context Product inv:
self.price_with_tax = self.tax*self.price_without_tax

Additional context

[ademait]

The alternative I proposed is only for the model (visual), since the OCL constraint can only be checked with the object model.

[jcabot]

Linked to #228