Re: XML DOM Binding for Ada 95 - matter of style

["Randy Brukardt" <randy@rrsoftware.com>]

"Matthew Heaney" <matthewjheaney@earthlink.net> wrote in message
news:Ly8Wa.716$jg7.380@newsread3.news.pas.earthlink.net...
> "Preben Randhol" <randhol+abuse@pvv.org> wrote in message
> news:slrnbihv85.4jd.randhol+abuse@kiuk0152.chembio.ntnu.no...
> > I thought one of the problems with Booch was that it was using tagged
> > types too much. Does Charles also use this approach?

You can't use tagged types too much. IMHO, virtually everything should be
derived from Controlled or Limited_Controlled (which by definition makes
them a tagged type). But...

> One problem is that you have to make two instantiations: one for the root
> package, in which the root type is declared, and another, for the child
> package in which the actual container (derived) type is declared.  This is
a
> royal pain.
>
> Charles deliberately avoided this technique, because no inheritance is
> necessary.  Static mechanisms are used instead, which are simpler and more
> general.

Right. *Inheritance* is what can easily be overused. It has its place, but
it can easily be overused. And users have a hard time understanding
"overriding", which is usually necessary to use these sorts of types.

We did Claw that way mainly because we wanted to be able to say that it was
"Object-Oriented"; if I was designing it with no marketing implications, we
may have chosen a different structure. (I'm not sure, because we never did
any analysis on non-O-O choices.)

In the specific case of container libraries, if it takes more than one
instantiation to get a basic container, it is too hard to use. If it's much
more complex than that, I'd rather build my own from scratch (none of them
are that much work to implement, especially as you almost never need the
full generality). And I don't think it is important to have a version for
every need. A version that works well for most needs is enough -- if you
have truly critical needs, you ought to build something custom that meets
those needs exactly. But most container needs aren't that critical. It's
more important to be able to use them to quickly build a solution that you
can profile to find out whether it is good enough or not.

                Randy.