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| Re: Single OCL constraint for multiple properties [message #517280 is a reply to message #517163] |
Fri, 26 February 2010 19:01  |
 Ed Willink
Messages: 7655
Registered: July 2009 |
Senior Member |
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Hi Timothy
This cannot be done in a typesafe Object Oriented language, you need a
'macro' facility such as C++ templates. Type safety requires that the
validity of xyz can be validated against XYZ.xyz, so A and B must
implement (in Java terms) XYZ. This does not require that they extend
(in Java terms) XYZ. XYZ is just a mix-in to define that A and B comply
with a common interface.
I have vaguely wondered whether OCL should support an extension
capability for inheritance as well as Properties and Operations. You
seem to provide a good justification for:
context XYZ
inv: self.xyz > 0
context A extends XYZ
context B extends XYZ
I'll raise an OMG issue.
Regards
Ed Willink
On 26/02/2010 12:49, Timothy Marc wrote:
> Hi all,
>
> i've a question concerning OCL for properties contained in different
> classifiers. Let's assume, we have two signals:
>
> Signal A {xyz:Integer}
> Signal B {xyz:Integer}
>
> Both properties are restricted by the same kind of constraint. In OCL i
> would use the following syntax:
>
> context A
> inv: self.xyz > 0
>
> context B
> inv: self.xyz > 0
>
> Since we have a lot of Signals, sharing similar properties, it is a
> quite annoying and repitive task to define these constraints in each
> signal separately. I know, generaliaztion might be the answer, but we
> didn't want the signals to be compatible with each other.
>
> In UML it is possible to define a constraint somewhere in the model and
> refer to elements which will be constrained by this single constraint.
> Is this also possible with OCL? If so, how does the syntax look like?
> Would the constraint point to the signals and than just state the
> invariant like this:
>
> self.xyz > 0
>
> Cheers and Thanks
> Timothy
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