Two interoperable implementations rule

[Maciej Stachowiak]

On Jul 14, 2008, at 1:46 PM, Mike Shaver wrote:

> On Mon, Jul 14, 2008 at 4:37 PM, Mike Cowlishaw <MFC at uk.ibm.com>  
> wrote:
>> (The decNumber code is quite stable, for example -- averaging fewer  
>> than one
>> detected bug/year since its first release in 2001, is used in  
>> numerous IBM,
>> SAP, and other vendors' products, and is part of the verification  
>> suite for
>> power.org, PowerPC, and IBM mainframe hardware.)
>
> I have no doubt; it's more whether the spec is sufficiently detailed
> and clear that someone can work from it and produce an interoperable
> implementation without using the same software impl.  Otherwise the
> spec can just include the decNumber source in an appendix, I guess. :)

I'd agree with the point of concern here. The risk is not bugs in  
decNumber but that the spec might not match what it does, or may not  
be sufficiently detailed to allow an independent interoperable  
implementation. However, if decNumber implements something specified  
in an independent standard (there's an IEEE standard for decimal  
floating point, isn't there?), then I don't think this should count  
against two implementations both using decNumber. For example, both  
Gecko and WebKit use ICU but I would still count them as independent  
implementations of HTML and CSS, since the shared component is only  
used to implement the underlying Unicode standard, not the HTML and  
CSS standards themselves.

Regards,
Maciej