[news.eclipse.modeling.mdt.uml2.ocl] Re: meaning of OCL getAppliedSubste

["Christian W. Damus" <cdamus@xxxxxxxxxx>]

Hi, Andy,

See some responses, in-line.

HTH,

Christian


Andreas Maier wrote:

> Hi,
> I am trying to understand what the OCL function
> getAppliedSubstereotype() does, because it looks like I can make use of
> it in some scenario.

This isn't so much an OCL operation as it is a UML operation that is
available to OCL because it is a "query."  :-)


> 
> The Eclipse UML2 description of the corresponding Java function reads:
> 
> -------------------------
> getAppliedSubstereotype
> 
> public Stereotype getAppliedSubstereotype( Stereotype stereotype,
>                                             String qualifiedName)
> 
> Retrieves the substereotype of the specified stereotype with the
> specified qualified name that is applied to this element, or null if no
> such stereotype is applied.
> -------------------------
> 
> Here are my questions:
> 
> 1. What is a "substereotype" ? A stereotype that is a specialization of
> another stereotype ?

Exactly.


> 2. I was trying to use the OCL function in a scenario where I am in a
> Class (OCL Context-wise), and want to go to a "substereotype" (using the
> assumption from above on what it is) of a stereotype that extends Class:
> 
> - Stereotype "CIM_Class" extends Class, and inherits from Stereotype
> "CIM_Qualifier_Abstract"
> 
> - The OCL constraint is owned by Stereotype "CIM_Class", and I tried
> (using some extra "let" expressions in order to test any intermediate
> results, due to lack of an OCL debugger ;-)
> 
> -------------------
> let mes : Stereotype =
>    self.base_Class.getAppliedStereotype('CIM::CIM_Class')
> in
> let qts : Stereotype =
>    self.base_Class.getAppliedSubstereotype( mes,
>      'CIM::CIM_Qualifier_Abstract')
> in
> mes <> null and mes.name = 'CIM_Class' /* (1) */
> and qts <> null and qts.name = 'CIM_Qualifier_Abstract' /* (2) */
> -------------------
> 
> The expression in line (1) succeeds, but the one in line (2) fails, so
> it seems I am either using this function in a wrong way, or it does not
> work as expected.

Yes, I think you are using it the wrong way  :-)

You would want to do:

   and qts <> null and qts.name = 'CIM_Class'

because CIM_Class is the specialization of CIM_Qualifier_Abstract that is
applied.  But, there's no reason to do this, because you already know (by
virtue of evaluating the constraint) that CIM_Class is applied.

> 
> I am aware that the generalization direction in my example is just the
> other way around, i.e. the OCL attempts to go to the super-stereotype,
> and that may already be the answer why it does not work. However I am
> having trouble to imagine a scenario where one would use the function to
> go to the sub-stereotype of one that was applied. Would the properties
> of such a sub-stereotype also be on the element that is extended by the
> super-stereotype ?

Right, you don't need to do any of this getAppliedSubstereotype, because the
specializing stereotype inherits all of the features of its general
stereotype(s).  All of the CIM_Qualifier_Abstract properties should be
directly accessible.

It's good that you're having trouble imagining a scenario in which the
super-stereotype has dependencies on particular sub-stereotypes, because
that would be an OO design mistake (dependency inversion)!  :-)

> 
> Andy