Re: Another take on versioning

"Toman_Vojtech@emc.com" <Toman_Vojtech@emc.com> writes:
>> I managed to convince myself that this wasn't actually a problem. Any
>> attempt to evaluate an unknown step will raise an error, so unless the
>> step occurs inside a p:when or the p:group of a p:try, the error can
>> propogate upwards. In a p:when or p:try, you know the order because
>> you have the other branches.
>
> I am not sure myself, but perhaps you are right.

I'm no longer in favor of this approach, but just to complete the loop
as it were...

> I still have to think
> about this. The biggest problem I have is that the V1 processor would
> have to assume too many things when it encounters a V2 step. Consider
> this pipeline:
>
> <p:pipeline>
>   <p:identity/>
>   <p:v2-step/>
> </p:pipeline>
>
> Now, let's assume the pipeline is a valid V2 pipeline, with no static
> errors. Then, in order to accept this pipeline statically, the V1
> processor must:
>
> 1. Assume that p:v2-step has a primary input port - otherwise err:XS0005
> (unconnected primary output port of p:identity) would be thrown
> 2. Assume that p:v2-step has a primary output port - otherwise
> err:XS0006 (primary output port of the pipeline not connected and the
> last step in the subpipeline does not have a primary output port)

I had a different approach in mind. The V1 processor sees p:v2-step:
that's going to fail dynamically. It's not inside a try/catch or a
choose/when, so the p:pipeline is going to fail dynamically as well.
So just report the dynamic error statically and never bother to try to
work out the flow graph.

> We should be very careful here, and really look at different scenarious
> where such kinds of assumptions may lead to unexpected behavior, or too
> ambitious requirements on V1 implementations.

Exactly. That's why I'm pulling back from this idea.

                                        Be seeing you,
                                          norm

-- 
Norman Walsh <ndw@nwalsh.com> | DNA neither cares nor knows. DNA just
http://nwalsh.com/            | is. And we dance to its music.--Richard
                              | Dawkins