Re: analysis of YANG vs. RELAX NG
Ladislav Lhotka <lhotka@cesnet.cz> Mon, 03 December 2007 14:33 UTC
Return-path: <discuss-bounces@apps.ietf.org>
Received: from [127.0.0.1] (helo=stiedprmman1.va.neustar.com) by megatron.ietf.org with esmtp (Exim 4.43) id 1IzCMV-0006bc-HM; Mon, 03 Dec 2007 09:33:31 -0500
Received: from discuss by megatron.ietf.org with local (Exim 4.43) id 1IzCMU-0006bA-6P for discuss-confirm+ok@megatron.ietf.org; Mon, 03 Dec 2007 09:33:30 -0500
Received: from [10.91.34.44] (helo=ietf-mx.ietf.org) by megatron.ietf.org with esmtp (Exim 4.43) id 1IzCMT-0006ax-ON for discuss@apps.ietf.org; Mon, 03 Dec 2007 09:33:29 -0500
Received: from office2.cesnet.cz ([195.113.144.244]) by ietf-mx.ietf.org with esmtp (Exim 4.43) id 1IzCMT-0007Sl-6D for discuss@apps.ietf.org; Mon, 03 Dec 2007 09:33:29 -0500
Received: from [198.18.175.153] (unknown [207.236.117.226]) by office2.cesnet.cz (Postfix) with ESMTP id C30B3D80098; Mon, 3 Dec 2007 15:33:25 +0100 (CET)
Subject: Re: analysis of YANG vs. RELAX NG
From: Ladislav Lhotka <lhotka@cesnet.cz>
To: j.schoenwaelder@jacobs-university.de
In-Reply-To: <20071203140846.GB17536@elstar.local>
References: <953beacc0711271504y7aea5f21jc301ccad886d3611@mail.gmail.com> <474D9194.3060103@ericsson.com> <953beacc0711281025w4d993dd7u77d729111074496c@mail.gmail.com> <20071128.230244.254578150.mbj@tail-f.com> <63F8A418-6AF0-4205-ACC7-53A8C7BC6A73@osafoundation.org> <47512728.6040201@gmx.de> <517bf110712021242v43c462f0v86267f591e5cdfbd@mail.gmail.com> <1196690162.5874.13.camel@missotis> <20071203140846.GB17536@elstar.local>
Content-Type: text/plain; charset="utf-8"
Organization: CESNET
Date: Mon, 03 Dec 2007 15:33:24 +0100
Message-Id: <1196692404.5874.36.camel@missotis>
Mime-Version: 1.0
X-Mailer: Evolution 2.12.1
Content-Transfer-Encoding: quoted-printable
X-Spam-Score: 0.0 (/)
X-Scan-Signature: 52f7a77164458f8c7b36b66787c853da
Cc: discuss@apps.ietf.org
X-BeenThere: discuss@apps.ietf.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: general discussion of application-layer protocols <discuss.apps.ietf.org>
List-Unsubscribe: <https://www1.ietf.org/mailman/listinfo/discuss>, <mailto:discuss-request@apps.ietf.org?subject=unsubscribe>
List-Post: <mailto:discuss@apps.ietf.org>
List-Help: <mailto:discuss-request@apps.ietf.org?subject=help>
List-Subscribe: <https://www1.ietf.org/mailman/listinfo/discuss>, <mailto:discuss-request@apps.ietf.org?subject=subscribe>
Errors-To: discuss-bounces@apps.ietf.org
Juergen Schoenwaelder píše v Po 03. 12. 2007 v 15:08 +0100: > On Mon, Dec 03, 2007 at 02:56:02PM +0100, Ladislav Lhotka wrote: > > Tim Bray p????e v Ne 02. 12. 2007 v 12:42 -0800: > > > I've been staying off this thread because I don't understand what a > > > NETCONF is or what you'd do with one. But Julian's point is massively > > > important. If you're going to design your own modeling language, you > > > need to spend a *lot* of time thinking about the extensibility model. > > > It's really easy to get wrong. -Tim > > > > Indeed. An extensibility problem in YANG is IMO the leaf statement. It > > is encoded as an XML element but the fact that it is declared as leaf > > effectively makes it into an XML attribute: It is impossible to extend > > it (e.g., add a qualifying subelement) without changing the leaf into > > container. In a RELAX NG schema, if properly designed, such an extension > > wouldn't have to touch the parent schema. > > Leafs carry data and we strongly dislike mixed contents in NETCONF. So > this is actually a YANG feature and not a bug. It doesn't necessarily mean mixed content, just changing <anel>XYZ</anel> into <anel> <anel-qual>ABC</anel-qual> <anel-value>XYZ</anel-value> </anel> Or, alternatively, the qualification info can be encoded in an attribute, which doesn't seem to be possible in YANG at all. I know, attributes are also frowned upon, but sometimes such a flexibility comes handy - and, after all, in some situations the extra attribute can be understood as metadata. > > > Another problem might be the default statement in leaves (or it is > > proper to say leafs here?:-) or typedefs. What if a standard data model > > defines an item, say a hello timer, with such a default, but an > > implementation wants to use another value for the default? Should it > > come up with another schema? > > No. There can only be one standard default. If you are thinking about > reusable groupings, then defaults can actually be changed wherever you > apply a grouping as far as I know. Protocols specifications in RFCS usually say that a particular default value SHOULD be something. So an impementation might have a reason for using something else. In such cases, the standard data model thus cannot use the default statement, right? Lada -- Ladislav Lhotka, CESNET PGP Key ID: E74E8C0C
- analysis of YANG vs. RELAX NG Rohan Mahy
- Re: analysis of YANG vs. RELAX NG Martin Bjorklund
- Re: analysis of YANG vs. RELAX NG Leif Johansson
- Re: analysis of YANG vs. RELAX NG Juergen Schoenwaelder
- Re: analysis of YANG vs. RELAX NG Juergen Schoenwaelder
- Re: analysis of YANG vs. RELAX NG Paul Hoffman
- RE: analysis of YANG vs. RELAX NG Natale, Bob
- Re: analysis of YANG vs. RELAX NG Lisa Dusseault
- Re: analysis of YANG vs. RELAX NG Rohan Mahy
- Re: analysis of YANG vs. RELAX NG Juergen Schoenwaelder
- RE: analysis of YANG vs. RELAX NG Romascanu, Dan (Dan)
- Re: analysis of YANG vs. RELAX NG Leif Johansson
- RE: analysis of YANG vs. RELAX NG Romascanu, Dan (Dan)
- Re: analysis of YANG vs. RELAX NG Martin Bjorklund
- Re: analysis of YANG vs. RELAX NG Jon Saperia
- Do we need a formalized language: [Was: Re: analy… Balazs Lengyel
- Re: analysis of YANG vs. RELAX NG Balazs Lengyel
- Re: analysis of YANG vs. RELAX NG Rohan Mahy
- Re: analysis of YANG vs. RELAX NG Martin Bjorklund
- Re: analysis of YANG vs. RELAX NG Rohan Mahy
- Re: analysis of YANG vs. RELAX NG Juergen Schoenwaelder
- Re: analysis of YANG vs. RELAX NG Martin Bjorklund
- Re: analysis of YANG vs. RELAX NG Lisa Dusseault
- Re: analysis of YANG vs. RELAX NG Rohan Mahy
- Re: analysis of YANG vs. RELAX NG Juergen Schoenwaelder
- Re: analysis of YANG vs. RELAX NG Phil Shafer
- Re: analysis of YANG vs. RELAX NG Juergen Schoenwaelder
- Re: analysis of YANG vs. RELAX NG Balazs Lengyel
- Re: analysis of YANG vs. RELAX NG Balazs Lengyel
- Re: analysis of YANG vs. RELAX NG Balazs Lengyel
- Re: analysis of YANG vs. RELAX NG Balazs Lengyel
- Re: analysis of YANG vs. RELAX NG Andrew Newton
- Re: analysis of YANG vs. RELAX NG Rohan Mahy
- Re: analysis of YANG vs. RELAX NG Rohan Mahy
- Re: analysis of YANG vs. RELAX NG Balazs Lengyel
- Re: analysis of YANG vs. RELAX NG Rohan Mahy
- Re: analysis of YANG vs. RELAX NG Randy Presuhn
- Re: analysis of YANG vs. RELAX NG Juergen Schoenwaelder
- Re: analysis of YANG vs. RELAX NG Martin Bjorklund
- Re: analysis of YANG vs. RELAX NG Andy Bierman
- Re: analysis of YANG vs. RELAX NG Julian Reschke
- Re: analysis of YANG vs. RELAX NG Tim Bray
- Re: analysis of YANG vs. RELAX NG Ladislav Lhotka
- Re: analysis of YANG vs. RELAX NG Juergen Schoenwaelder
- Re: analysis of YANG vs. RELAX NG Ladislav Lhotka
- Re: analysis of YANG vs. RELAX NG Juergen Schoenwaelder
- Re: analysis of YANG vs. RELAX NG Andy Bierman
- Re: analysis of YANG vs. RELAX NG Ladislav Lhotka
- Re: analysis of YANG vs. RELAX NG Andy Bierman
- Re: analysis of YANG vs. RELAX NG Randy Presuhn
- RE: analysis of YANG vs. RELAX NG David Harrington
- RE: analysis of YANG vs. RELAX NG Romascanu, Dan (Dan)
- Re: analysis of YANG vs. RELAX NG Ladislav Lhotka
- Re: analysis of YANG vs. RELAX NG Juergen Schoenwaelder
- Re: analysis of YANG vs. RELAX NG Balazs Lengyel