RE: analysis of YANG vs. RELAX NG

"Romascanu, Dan (Dan)" <dromasca@avaya.com> Mon, 03 December 2007 22:14 UTC

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Subject: RE: analysis of YANG vs. RELAX NG
Date: Mon, 3 Dec 2007 23:12:50 +0100
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From: "Romascanu, Dan (Dan)" <dromasca@avaya.com>
To: "Ladislav Lhotka" <lhotka@cesnet.cz>, "Andy Bierman" <ietf@andybierman.com>
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> -----Original Message-----
> From: Ladislav Lhotka [mailto:lhotka@cesnet.cz] 
> Sent: Monday, December 03, 2007 8:02 PM
> To: Andy Bierman
> Cc: discuss@apps.ietf.org
> Subject: Re: analysis of YANG vs. RELAX NG
> 
> 
> Andy Bierman píše v Po 03. 12. 2007 v 09:21 -0800:
> 
> > I strongly agree with Juergen.
> > YANG is based (in part) on 18+ years experience with SNMP and SMI.
> 
> And ignoring the additional flexibility XML can provide.
> 
> > 
> > It s absolutely forbidden in NM to redefine the syntax and 
> semantics 
> > of a managed object in this way.
> 
> Why? Even if I explicitly specify I am using another data 
> model? The difference is that if the data model is easily 
> extensible, I can just write
> 
> import parent-model;
> 
> and then 5 lines or so describing the differences, so that it 
> is immediately clear what I am doing (and hopefully why). If 
> the extensibility is weak, I have to take the parent model, 
> change few lines and declare it as a new data model - but the 
> differences are not that clear.
> 
> Lada
>  
> --
> Ladislav Lhotka, CESNET
> PGP Key ID: E74E8C0C
> 
>

Lada,

How can two different management entities interoperate if the same object has two different semantics because they have loaded two different versions of the data model? Only the entity that has loaded the newer version will be aware about the ' 5 lines or so describing the differences', what about the older one? 

Dan
(asking as contributor)