From: "Weirich, James" <James.Weirich@...>
Date: 2003-11-20T05:37:02+09:00
Subject: Re: "stereotyping" (was: Re: Strong Typing (Re: Managing metadata	 about attribute types) )

From: Austin Ziegler [mailto:austin@halostatue.ca] 
> Anecdotally, I did some work with Ruwiki recently and Chad Fowler
> created a mock object to make the Ruwiki tokenizing process think
> that it was dealing with an instance of Ruwiki. That mock object has
> become part of Ruwiki's object hierarchy, although not as Chad
> defined it. (I abstracted the data that Chad was using into its own
> object.) If I had done ancestry checking initially, Chad wouldn't
> have been able to do this.

I think this is a strong example of what we are talking about.  Checking for
a concrete Ruwiki object would have prevented this kind of generalization.
Some might say that you shouldn't check against a concrete object anyways,
but should be using an abstract object.  The point is that at the point Chad
was experimenting with Ruwiki, there was no abstract object.  The Ruwiki
programmer had no need to create an abstraction, and indeed would have been
hard pressed to create one (usable by Chad) without understanding Chad's
needs (which weren't defined at the point Ruwiki was written).  Explicit
ancestry checking makes this kind of development more difficult.

And I wish to emphasize that this is not an isolated incident.  This happens
all the time in the test frameworks I tend to develop with my Ruby programs.


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