Re: [mdt-ocl.dev] Overload resolution and dynamic dispatch patch

[Ed Willink <ed@xxxxxxxxxxxxx>]

Hi Axel

I think you're confusing two different issues.

a) impact for unloaded Resources
b) impact through polymorphic calls

a) unloaded Resources

In your earlier example with resource Y (unloaded) so that propagation 
of 42 through resource X failed to impact:

Using my dependency analysis perspective, if the Y resource is not 
loaded, I don't analyze it, I don't detect any dependencies, so I don't 
install any listeners/notifiers to cause the Y resource elements to 
react to changes. So I agree that it doesn't work. It's nothing to do 
with EMF-based; it's just common sense.

Consider a doctor's patient list and the impact of a policy change to 
invite all patients over 50 rather than over 60 to have a free flu 
vaccination for the winter. The derived property of the number of 
required injections can only be determined by examining each patients 
records. If a patient's record is not loaded into the system/looked at 
by a human, the accurate answer cannot be determined. It seems 
unreasonable to expect to have impact or dependencies for unloaded 
resources.

b) polymorphic calls

It seems that your traceback does not use the source object and so needs 
to consider all possible operations.  This seems inefficient and may 
lead to fat notifications that can be filtered. The dependency 
perspective knows the source object and so need only consider the 
relevant operation.

    Regards

        Ed

On 07/05/2012 10:55, Axel Uhl wrote:
> We may consider adjusting the impact analyzer by granting it access to 
> the dynamic dispatch cache. It may, however, lead to a situation where 
> an operation hasn't been evaluated in a given environment yet, hence 
> no cache entry is present for the operation, and hence the look up 
> would provide the IA with too few operation bodies to analyze.
>
> I claim that generally, without having evaluated all expressions on 
> all objects, ensuring that all relevant operation bodies have been 
> evaluated at least once, no EMF-based approach can determine a change 
> impact because expressions affected by the change may simply not be 
> known by the environment.
>
> A cleaner, probably not entirely satisfying approach may involve 
> equipping the IA with a set of EPackage objects which define the 
> "universe" of metamodels to be considered by the IA. The IA could 
> then, at some start-up cost, determine the operation bodies to be 
> considered.
>
> Opinions?
>
> -- Axel