Re: [netmod] Y34

[Lou Berger <[e-mail]>]

Andy,

Have you thought through implications / possibilities for existing models,  
e.g., interfaces?

Thanks,
Lou


On July 26, 2015 4:41:32 PM Andy Bierman <[e-mail]> wrote:

> Hi Acee,
>
> I agree that "Relocatable YANG" would be very useful, and have been
> thinking about the problem for awhile.  I think the key is to precisely
> define a protocol-independent document root for each of the various
> YANG XPath contexts.  In most cases the expression can be
> automatically relocated to an ancestor root.  For the rest, a
> YANG mechanism is needed to tell the compiler to force evaluation
> on the old docroot (not the new docroot ancestor).
>
>
> Andy
>
>
> On Sun, Jul 26, 2015 at 10:49 AM, Acee Lindem (acee) <[e-mail]> wrote:
>
> > I think being able to place a given model anywhere in the device tree
> > would be useful and this would allow a model to be rooted in different
> > locations on different devices. Similarly, we’d need the ability to prefix
> > XPATH references to data nodes in the model with the root.
> > Thanks,
> > Acee
> >
> > On 7/20/15, 11:00 PM, "netmod on behalf of Juergen Schoenwaelder"
> > <[e-mail] on behalf of
> > [e-mail]> wrote:
> >
> > >Lada,
> > >
> > >Y34 is closed and I have not seen any new argument here that indicates
> > >we made a major mistake with the resolution of Y34. As such, Y34
> > >remains closed.
> > >
> > >If you want to discuss new ideas to relocate or "symlink" data models,
> > >please do so in a separate thread. (And no, we do not accept new
> > >issues for YANG 1.1 either at this point in time.)
> > >
> > >/js
> > >
> > >On Mon, Jul 20, 2015 at 07:42:49PM +0200, Ladislav Lhotka wrote:
> > >>
> > >> > On 20 Jul 2015, at 19:29, Andy Bierman <[e-mail]> wrote:
> > >> >
> > >> >
> > >> >
> > >> > On Mon, Jul 20, 2015 at 10:15 AM, Ladislav Lhotka <[e-mail]>
> > >>wrote:
> > >> >
> > >> > > On 20 Jul 2015, at 17:00, Andy Bierman <[e-mail]> wrote:
> > >> > >
> > >> > >
> > >> > >
> > >> > > On Mon, Jul 20, 2015 at 6:08 AM, Ladislav Lhotka <[e-mail]>
> > >>wrote:
> > >> > >
> > >> > > > On 20 Jul 2015, at 14:55, Andy Bierman <[e-mail]>
> > wrote:
> > >> > > >
> > >> > > > Hi,
> > >> > > >
> > >> > > > Can you explain why we need 2 broken anyxmls?
> > >> > > > (The original and a synonym?)  The whole point of
> > >> > > > anydata is that it does not have XML cruft in it.
> > >> > >
> > >> > > Yes, I understand this was your main priority. For implementors
> > >>using off-the-shelf XML parsers and tools the XML cruft is not an issue
> > >>at all.
> > >> > >
> > >> > >
> > >> > > yes it is an issue.
> > >> > > We need something to model a container full of arbitrary YANG data
> > >>nodes.
> > >> > > This is something that can be applied to the contents of a
> > >>datastore.
> > >> >
> > >> > anyxml can do that, too.
> > >> >
> > >> >
> > >> > the WG already decided it can't.
> > >> > The extra XML PIs, etc. are not accepted by all servers, remember?
> > >> > There is no use for the extra stuff in the datastore.
> > >> >  I don't see why we need 2 anyxml constructs that are not
> > >> > supported by the industry.  One is already too many.
> > >>
> > >> I agree, but this is what we are going to have. My proposal was to have
> > >>just one with two different names.
> > >>
> > >> >
> > >> >
> > >> > >
> > >> > >
> > >> > > Anyway, I believe there are use cases for arbitrary XML/JSON/CBOR/…
> > >>with no (YANG) schema available. My only complaint to “anyxml” has
> > >>always been that it is a misnomer for encodings other than XML.
> > >> > >
> > >> > > The message encoding on the wire is not the same issue
> > >> > > as the contents of a datastore.  Our server stores its own
> > >> > > internal data structures.  XML, JSON, CBOR are just message
> > >> > > encoding formats between client and server.  The datastore
> > >> > > is not encoded in any of these formats.
> > >> >
> > >> > The payload of anyxml needn’t directly map to a data subtree in the
> > >>usual sense.
> > >> >
> > >> > that's precisely the difference between anyxml and anydata.
> > >> > The anydata node MUST map directly into data subtrees.
> > >>
> > >> If the server doesn’t know the YANG data model at run time (which is
> > >>possible) then it cannot do it - for instance, it cannot properly map
> > >>module names to namespace URI or handle lists.
> > >>
> > >> >
> > >> >
> > >> >
> > >> > >
> > >> > >
> > >> > >
> > >> > >
> > >> > >
> > >> > > >
> > >> > > > I also don't get the value of a single top-level node called
> > >>'device'
> > >> > > > that every YANG model on the planet is supposed to augment.
> > >> > > > Can you explain why a protocol operation to retrieve the
> > >> > > > document root (/) is not sufficient for the top-level node?
> > >> > >
> > >> > > I don’t intend to defend their model, the more serious problem IMO
> > >>is that a model for a single device/function may be needed in another
> > >>device that hosts many virtualised devices/functions of the former type.
> > >>We don’t have a good solution for this rather typical situation.
> > >> > >
> > >> > > But a single container called "whatever" provides no such
> > >>aggregation.
> > >> > > You would need a list for that. And the NMS might have multiple
> > >> > > layers of hierarchy to represent various aggregations.  The NP
> > >> > > container called "device" is not helpful for aggregation.
> > >> >
> > >> > The parent node can be a list as well. The “root” node would be like
> > >>a mount point in a Unix filesystem.
> > >> >
> > >> >
> > >> > Are you saying all data on a device needs to be in a top-level list
> > >>called 'device'
> > >> > because an NMS might exist that  wants to have the datastores from
> > >>lots of devices?
> > >> > As Martin pointed out several times, the NMS can make its own
> > >>container or
> > >> > lists.  It does not need the device to mirror its own structure.
> > >>
> > >> As I said, I don’t care that much about the “device” container. What
> > >>would be really useful is to have the possibility to do e.g. this:
> > >>
> > >> virtual-node* [name]
> > >>     name
> > >>     if:interfaces
> > >>         ...
> > >>
> > >> to support the use case where all virtual nodes are managed by the same
> > >>NETCONF/RESTCONF server.
> > >>
> > >> Lada
> > >>
> > >> >
> > >> >
> > >> >
> > >> > Lada
> > >> >
> > >> > Andy
> > >> >
> > >> >
> > >> > >
> > >> > >
> > >> > >
> > >> > > Lada
> > >> > >
> > >> > >
> > >> > > Andy
> > >> > >
> > >> > >
> > >> > > >
> > >> > > > Andy
> > >> > > >
> > >> > > >
> > >> > > >
> > >> > > > On Mon, Jul 20, 2015 at 5:48 AM, Ladislav Lhotka <[e-mail]>
> > >>wrote:
> > >> > > >
> > >> > > > > On 20 Jul 2015, at 14:45, Ladislav Lhotka <[e-mail]>
> > wrote:
> > >> > > > >
> > >> > > > > Hi,
> > >> > > > >
> > >> > > > > after listening to the presentation of
> > >> > > > > draft-rtgyangdt-rtgwg-device-model-00 at RTGWG session, I am
> > >>wondering
> > >> > > > > whether the solution chosen for Y34 is really useful.
> > >> > > > >
> > >> > > > > The draft states they want to reuse ietf-interfaces but their
> > >>tree in
> > >> > > > > fact is
> > >> > > > >
> > >> > > > >   +--rw device
> > >> > > > >          +--rw info
> > >> > > > >          |  +--rw device-type?   enumeration
> > >> > > > >          +--rw hardware
> > >> > > > >          +--rw interfaces
> > >> > > > >          |  +--rw interface* [name]
> > >> > > > >          |     ...
> > >> > > > >          +--rw qos
> > >> > > > >
> > >> > > > > So the "interfaces" container is no more a top-level node.
> > >>There are
> > >> > > > > three possible options:
> > >> > > > >
> > >> > > > > 1. Change the ietf-interfaces module.
> > >> > > > > 2. Replicate its contents in another module.
> > >> > > > > 3. Extend YANG so that a *specific* schema tree can be grafted
> > >>at a
> > >> > > > >   given data node.
> > >> > > > >
> > >> > > > > IMO #1 & #2 are really bad. I thought Y34-04 was essentially #3
> > >>but it
> > >> > > > > seems it is not so because it doesn't specify a concrete data
> > >>model
> > >> > > > > that's allowed at a given location.
> > >> > > > >
> > >> > > > > On the other hand, the only real contribution of "anydata" over
> > >>"anyxml"
> > >> > > > > is that is doesn't permit mixed content in XML, which is IMO
> > >>not much.
> > >> > > > >
> > >> > > > > I know Y34 was already closed but I think it is more important
> > >>to do
> > >> > > > > things right before YANG 1.1 becomes an RFC.
> > >> > > > >
> > >> > > > > What I want to propose is this:
> > >> > > > >
> > >> > > > > - Rename "anydata" as a synonym to "anyxml", and deprecate
> > >>"anyxml" (but
> > >> > > > >  keep it for backward compatibility).
> > >> > > >
> > >> > > > s/Rename/Introduce/
> > >> > > >
> > >> > > > >
> > >> > > > > - Introduce a new statement and data node type, e.g. "root",
> > >>that will
> > >> > > > >  extend the schema tree starting from that data node with a
> > >>precisely
> > >> > > > >  specified data model. The specification can be same or similar
> > >>as
> > >> > > > >  in yang-library.
> > >> > > > >
> > >> > > > > I believe there are other use cases in the existing modules. For
> > >> > > > > example, the ietf-routing module could simply define the data
> > >>model for
> > >> > > > > a single routing instance (i.e. without "routing-instance" list
> > >>at the
> > >> > > > > top), and it can be then used without changes on simple
> > >>devices, and
> > >> > > > > more complex router implementations can graft it as a subtree
> > >>under
> > >> > > > > "routing-instance", "networking-instance" or whatever.
> > >> > > > >
> > >> > > > > Lada
> > >> > > > >
> > >> > > > > --
> > >> > > > > Ladislav Lhotka, CZ.NIC Labs
> > >> > > > > PGP Key ID: E74E8C0C
> > >> > > > >
> > >> > > > > _______________________________________________
> > >> > > > > netmod mailing list
> > >> > > > > [e-mail]
> > >> > > > > https://www.ietf.org/mailman/listinfo/netmod
> > >> > > >
> > >> > > > --
> > >> > > > Ladislav Lhotka, CZ.NIC Labs
> > >> > > > PGP Key ID: E74E8C0C
> > >> > > >
> > >> > > >
> > >> > > >
> > >> > > >
> > >> > > > _______________________________________________
> > >> > > > netmod mailing list
> > >> > > > [e-mail]
> > >> > > > https://www.ietf.org/mailman/listinfo/netmod
> > >> > > >
> > >> > >
> > >> > > --
> > >> > > Ladislav Lhotka, CZ.NIC Labs
> > >> > > PGP Key ID: E74E8C0C
> > >> > >
> > >> > >
> > >> > >
> > >> > >
> > >> > >
> > >> >
> > >> > --
> > >> > Ladislav Lhotka, CZ.NIC Labs
> > >> > PGP Key ID: E74E8C0C
> > >> >
> > >> >
> > >> >
> > >> >
> > >> > _______________________________________________
> > >> > netmod mailing list
> > >> > [e-mail]
> > >> > https://www.ietf.org/mailman/listinfo/netmod
> > >>
> > >> --
> > >> Ladislav Lhotka, CZ.NIC Labs
> > >> PGP Key ID: E74E8C0C
> > >>
> > >>
> > >>
> > >>
> > >> _______________________________________________
> > >> netmod mailing list
> > >> [e-mail]
> > >> https://www.ietf.org/mailman/listinfo/netmod
> > >
> > >--
> > >Juergen Schoenwaelder           Jacobs University Bremen gGmbH
> > >Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
> > >Fax:   [phone]         <http://www.jacobs-university.de/>
> > >
> > >_______________________________________________
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> >
> > _______________________________________________
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> >
>
>
>
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