RE: [xml-dev] Too much power? was RE: [xml-dev] 2007 Predictions

[noah_mendelsohn@us.ibm.com]

Mike Champion writes:

> (I can't remember why the TAG changed "Principle"
to "Rule" in the 
> title).  "The Rule of Least Power" sounds a lot more
awesome than 
> the actual advice being offered really is.

I don't think it's been discussed here, and I don't
think the change merits more discussion.  In short:  TimBL originally
called it the Principle of Least Power, which I liked a lot.  Years
went by, and in other work such as the Archticture of the World Wide Web
[1] the TAG decided there was value in making fairly careful use of certain
terminology [2]:

Principle
An architectural principle is a fundamental rule that
applies to a large number of situations and variables. Architectural principles
include "separation of concerns", "generic interface",
"self-descriptive syntax," "visible semantics," "network
effect" (Metcalfe's Law), and Amdahl's Law: "The speed of a system
is limited by its slowest component."
Constraint
In the design of the Web, some choices, like the names
of the p and li
elements in HTML, the choice of the colon (:) character in URIs, or grouping
bits into eight-bit units (octets), are somewhat arbitrary; if paragraph
had been chosen instead of p
or asterisk (*) instead of colon, the large-scale result would, most likely,
have been the same. This document focuses on more fundamental design choices:
design choices that lead to constraints, i.e., restrictions in behavior
or interaction within the system. Constraints may be imposed for technical,
policy, or other reasons to achieve desirable properties in the system,
such as accessibility, global scope, relative ease of evolution, efficiency,
and dynamic extensibility.
Good practice
Good practice—by software developers, content authors,
site managers, users, and specification designers—increases the value
of the Web.

So, somebody made the case that the XXX of Least Power
was in not quite a Principle but was really more of a Good Practice.  Then
again, calling a TAG finding the "Good Practice of Least Power"
didn't have a real catchy ring to it.  So, for better or worse, as
a compromise, we renamed the finding itself the "Rule of Least Power".
 I don't love it.  Probably nobody loves it, but there you go.
 FWIW, the finding does have in it the following [3]:

        Principle:
Powerful languages inhibit information reuse. 
        
...because that did seem closer to being a principle,
and a Good Practice Note [4]:

        Good Practice:
Use the least powerful language suitable for expressing information, constraints
or programs on the World Wide Web. 

Since you asked, that's how it came to be.  I
don't think the particular question of Rule vs. Principle, etc. is worth
further discussion on this list.

Noah


[1] http://www.w3.org/TR/webarch/
[2] http://www.w3.org/TR/webarch/#app-principles
[3] http://www.w3.org/2001/tag/doc/leastPower.html#plp
[4] http://www.w3.org/2001/tag/doc/leastPower.html#ruleOfLeastPower

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Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
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