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Re: Mailmen, POST, Intent, and Duck Typing

• To: xml-dev@l...
• Subject: Re: Mailmen, POST, Intent, and Duck Typing
• From: Jan Algermissen <jalgermissen@t...>
• Date: Fri, 24 Feb 2006 16:32:41 +0100
• In-reply-to: <15725CF6AFE2F34DB8A5B4770B7334EE0BB1FEDF@h...>
• References: <15725CF6AFE2F34DB8A5B4770B7334EE0BB1FEDF@h...>

Hi,

On Feb 24, 2006, at 3:41 PM, Bullard, Claude L ((Len)) wrote:

> It's like
> asking your mailman to do your taxes instead of moving the
> form to the IRS and bringing the payment back.

To extend the analogy:

There is your mailman and your tax consultant, both having a  
processThis() method.
You send you tax stuff to the tax consultant because you know it is a  
tax consultant and you send your mail to your mail man because you  
know that it is a mailman.

But the give-stuff-to-operation is uniform ("take this and do what  
your job is"), I do not have to know about a processMail() or  
processTaxStuff() method.

If the mailman changes jobs and you still hand him your mail (say  
because he happens to live in the same street now and passes by)  
he'll be able to respond: "No, go away...that ain'y my business anymore"

Aside: the 'that' in the last sentence implies that the (former)  
mailman understands your intent.

I wonder if it is sufficient for the receiver to infer the intent  
from recognizing what the stuff is that you handed to him (e.g. looks  
like mail => must be mail[1]) or if a protocol mechanism is needed  
such as HTTP's Expect header.

If not, the out of band coordination (besides the protocol) would be  
reduced to a shared (loose?) understanding of what mail is.

Thoughts welcome.

Jan

[1] Aka "Duck Typing":
     http://www.propylon.com/news/ctoarticles/040224_duckmodeling.html


________________________________________________________________________ 
_______________
Jan Algermissen, Consultant & Programmer                         
http://jalgermissen.com
Tugboat Consulting, 'Applying Web technology to enterprise IT'   
http://www.tugboat.de

• References:
  • RE: Did Documents Win? No. Objects Just Couldn't GetTheir Act Together.
    • From: "Bullard, Claude L \(Len\)" <len.bullard@i...>

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