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Re: Does the W3C allow "reference implementations"?

• From: David Carlisle <davidc@nag.co.uk>
• To: "Costello, Roger L." <costello@mitre.org>
• Date: Wed, 24 Nov 2010 14:11:05 +0000

On 24/11/2010 13:29, Costello, Roger L. wrote:
 > Hi Folks,
 >
 > I just read this:
 >
 >      ISO officially does not allow reference implementations
 >
 > Here's where I read it:
 >
 >      http://www.schematron.com/implementation.html
 >
 > See the 2nd sentence of the 2nd paragraph.
 >
 > The author of that web page is Rick Jelliffe, who is the author of 
several ISO standards.
 >
 > This got me wondering, "Does the W3C allow reference implementations?"

no

 >
 > I know that the W3C requires a specification have a certain number of
implementations before the specification can become a full
Recommendation. Does the W3C consider them to be "reference
implementations"?

Not exactly. the exact rules are stated for each specification's last 
call document draft, but often the requirement is that each feature has 
two implementations, not that two implementations implement the entire 
spec.  The purpose of the implementation requirement at W3C is to show 
that the spec is _implementable_  not that it has been fully _implemented_.

 > What is the rationale for not allowing reference implementations?

It maintains the authority of the written specification.

If implementations differ from the spec in edge cases (which always 
happens) then it is clear that later implementations should try to do 
better and match the written spec. If on the other hand there is a 
reference implementation, then later implementations try to match that.

Of course that happens anyway with pdf implementations mimicking adobe 
acrobat reader, even where it doesn't follow the spec, and html 
implementations mimicking IE. Declaring acrobat (or IE) a "reference" 
implementation would just encourage such reverse engineering.

 >
 > /Roger

David


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• References:
  • Does the W3C allow "reference implementations"?
    • From: "Costello, Roger L." <costello@mitre.org>