RE: [xml-dev] Include data that may be objectively generated some day?

["David Lee" <dlee@calldei.com>]

I think "Foresight" is the key.  Fundamentally this is the same
problem/question on any DB/Data language/platform.  What is the effect of
adding an unused "future" field to say
* A relational Table
* A C++ or Java object
* A method signature
* A paper form
* A contact 
* Your desk drawer
* A wall outlet
* A standard connector (DB25 etc. ...)

The difference, IMHO, with XML is in the greater likelihood of data
*interchange* ... although it may be similar to say a field in a web
service.

My opinion

1) Unless you *are absolutely certain* what this field will be in the future
and how it is supposed to be interpreted, and is documented.  Don't do it.

2) If you do it,  make it *optional* so that document instances do not have
to populate this "future" field/attribute.

3) Create a V1 schema which makes the field required to be empty (???)
OR
4) Why not simply omit it from the V1 schema ? and add it later if needed ?

5) Don't do it.




----------------------------------------
David A. Lee
dlee@calldei.com
http://www.xmlsh.org

-----Original Message-----
From: Michael Kay [mailto:mike@saxonica.com] 
Sent: Monday, November 28, 2011 12:41 PM
To: xml-dev@lists.xml.org
Subject: Re: [xml-dev] Include data that may be objectively generated some
day?


 >More generally, what will be the consequence of adding this element to 
the Book XML vocabulary?

It's an open invitation to tag abuse: someone will discover that nothing 
breaks if they use this field to hold a readability metric for the book, 
and so they will use it for that, or for something else.

Of course, "tag abuse" is a loaded term. I have seen examples where tag 
abuse delivered superb new functionality in a system at very low cost. 
But perhaps that could have been achieved without tag abuse if the 
designers had had more foresight.

Michael Kay
Saxonica


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