Re: [netmod] schema-mount pre09 branch

Ladislav Lhotka <lhotka@nic.cz> Wed, 07 February 2018 12:18 UTC

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From: Ladislav Lhotka <lhotka@nic.cz>
To: Robert Wilton <rwilton@cisco.com>, netmod@ietf.org
Date: Wed, 07 Feb 2018 13:18:26 +0100
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Subject: Re: [netmod] schema-mount pre09 branch
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On Wed, 2018-02-07 at 11:41 +0000, Robert Wilton wrote:
> 
> On 07/02/2018 10:29, Ladislav Lhotka wrote:
> > On Wed, 2018-02-07 at 11:14 +0100, Martin Bjorklund wrote:
> > > Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de> wrote:
> > > > On Tue, Feb 06, 2018 at 03:25:52PM +0000, Robert Wilton wrote:
> > > > > I think that the term "external" could also be confusing, since I
> > > > > think
> > > > > that
> > > > > sort of implies peer mount like semantics.
> > > > 
> > > > The "inline" mount concept seems to subsume peer mounts. From the
> > > > model perspective, is there a difference whether the mounted data is
> > > > local or remote (and what does local/remove mean for a VM)?
> > > >   
> > > > > I would suggest the term "dynamic" instead of "inline " but that could
> > > > > easily be confused with dynamic datastores.
> > > > 
> > > > Yes, I think this is not a good word either.
> > > > 
> > > > > Perhaps rather than "inline" another choice could be "discoverable",
> > > > > i.e.
> > > > > the schema is not known, and is dynamically discoverable inline at the
> > > > > mount
> > > > > point.
> > > > > Equally, rather than "use-schema", perhaps a better choice would be
> > > > > "known",
> > > > > i.e. the schema is already known, and made available as part of YANG
> > > > > library.
> > > > 
> > > > Perhaps integrated schema vs. mounted schema.
> > > 
> > > I like the term "integrated" better than "use-schema".  But both cases
> > > are mounted, so we need another term than "mounted" for "inline".
> > > "segregated" doesn't sound quite right ;-)
> > 
> > I would prefer to use the term "mount" only for the inline case and find
> > something else for the use-schema case. The term "mount" evokes that some
> > *instance* data being added, which is what happens in the "inline" case but
> > not
> > for "use-schema".
> 
> Perhaps the "use-schema" case really is a type of "schema mount", where 
> as the "inline" case is a type of "mount".

This may be quite confusing. My suggestion for "use-schema" is "external
augment" - the mount point as a *schema node* plays a very similar role to the
target node of an augment.

> 
> Perhaps they could/should have entirely separate YANG models to describe 
> them.  Possibly in the "use-schema" case could refer to grafting a 
> schema into a parent schema rather than mounting it.

I proposed this previously. The inline case could in fact be considerably
simplified because the extension statement is all that's needed - no state data.
In other words, the "mount-point" extension would immediately indicate the
inline mount.  

In order to distinguish the use-schema case (or whatever we call it) we have
then two options:

1. use a different YANG extension for labelling mount points of this type

2. use schema node identifiers as in augments (i.e. no extension at all).

Thanks, Lada

> 
> Thanks,
> Rob
> 
> 
> > 
> > Lada
> > 
> > > 
> > > /martin
> > > 
> > > > > Whether it would be right to change these at this time, I've no idea
> > > > > ...
> > > > 
> > > > Yep.
> > > > 
> > > > /js
> > > > 
> > > > -- 
> > > > Juergen Schoenwaelder           Jacobs University Bremen gGmbH
> > > > Phone: +49 421 200 3587         Campus Ring 1 | 28759 Bremen | Germany
> > > > Fax:   +49 421 200 3103         <https://www.jacobs-university.de/>
> > > > 
> > > 
> > > _______________________________________________
> > > netmod mailing list
> > > netmod@ietf.org
> > > https://www.ietf.org/mailman/listinfo/netmod
> 
> 
-- 
Ladislav Lhotka
Head, CZ.NIC Labs
PGP Key ID: 0xB8F92B08A9F76C67