[cad-linux-dev] Re: polymorphic inheritance
- From: Eric Wilhelm <ewilhelm@xxxxxxxxxxxxx>
- To: CAD linux development <cad-linux-dev@xxxxxxxxxxxxx>
- Date: Wed, 25 Aug 2004 06:36:23 -0500
# The following was supposedly scribed by
# Bruno Postle
# on Wednesday 25 August 2004 05:47 am:
>> I think anything to do with inheritance and references takes us
>> too far towards relational drafting. =A0That doesn't fit the
>> rhizopod model.
>
>Yes, none of this has any relevance when using a hub as an
>intermediary between existing CAD tools.
>
>Though the other litmus test of a "good idea" is that it makes
>possible things that were never possible before.
It is a good idea, but it's also incompatible with the existing constraints.
>> So, are you already designing the "sardine" spec here?
>
>No, I'm designing an extension to the spec for the 'reference'
>object,=20
I'm afraid rhizopod isn't extensible.
>I want everything else to be identical to rhizopod. =A0If I=20
>can tag these extended reference elements with "version: foo", then
>your library will know not to bother interpreting them=20
But 'grep' wasn't compiled with my library.
>- It will=20
>spit out a warning and won't core dump on people.
That's possible, but I'd prefer to not have strange speedbumps laying aroun=
d=20
in my rhizopod directories.
Let's take your subclass idea and apply it to the spec:
=46or argument's sake, Draft is using the 'sardine' spec, which is a slight=
=20
evolution of rhizopod that supports references with polymorphic inheritance=
=2E =20
Otherwise, it is identical. With that, a simple connector that doesn't=20
support polymorphic references is my hop_to_links program (which makes=20
directory trees of symlinks to individual files.) A better connector would=
=20
interpolate the references of the sardine format into static forms that wou=
ld=20
be readable in the rhizopod format.
http://ericwilhelm.homeip.net/svn/Module-Subversion-Juggle/trunk/data/scrip=
ts/
Maybe sardine is more extensible than rhizopod, and maybe rhizopod eventual=
ly=20
becomes sardine (that is, all of its connectors switch to using sardine), b=
ut=20
I think it's better to have at least a one-way data path rather than having=
=20
the postscript connector ignore your brave new entities (you want to be abl=
e=20
to print them right?)
=2D-Eric
=2D-=20
"Everything goes wrong all at once."
--Quantized Revision of Murphy's Law
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