Design Patterns discussion

["Thomas Mercer-Hursh, Ph.D." <thomas AT cintegrity.com>]

David Rosenstrauch wrote:
>  Sorry for the late response.

Seems like one should be grateful for any response on this list these 
days...

>  Quintessential example of this would be, say, the InputStream and
>  OutputStream families of I/O objects in Java.  You take any "vanilla"
>  stream object (e.g., that writes to a file, a socket, etc.) and then
>  add functionality onto it by wrapping it in decorator streams - e.g.,
>  BufferedOutputStream, PrintStream, etc.

I'm familiar with usage like this and have poked around at a number of 
sources.  All of them that I find are consistent with this notion of 
dynamic addition of behavior to individual objects, i.e., places where 
Generalization and/or Delegation would not necessarily work well since 
those are static decompositions.  What I was wondering about is whether 
there was any support for this fellow's approach of using this pattern 
as a routine substitute for what would normally be done by 
Generalization and/or Delegation.

FWIW, my write-up on the topic has been completed and can be found here:
http://www.cintegrity.com/content/%E2%80%9CGang-Four%E2%80%9D-Decorator-Pattern-What-Its-Appropriate-Use
I should probably note that my focus in general is on OO as it should be 
practiced in ABL, the Progress 4GL, so a bit different than the 3GL 
world, although I believe the same principles should be applied and this 
particular discussion seems to me to be independent of the 
implementation language.
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Thomas Mercer-Hursh, Ph.D.            email: 
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