Re: [core] ? WG adoption of draft-veillette-core-yang-cbor-mapping-00

[Somaraju Abhinav <[e-mail]>]

Hi,
We have been using YANG to model objects that we use with LWM2M for about 6 months now. As far as I can tell, there is only one part of the LWM2M resource model that cannot be modelled using YANG: LWM2M has resources on which you can read, write and execute (operations). YANG distinguishes between resources that are operations vs data and therefore cannot be used to model resources in LWM2M that support the three types of operations. There are of course ways around this issue.

As an example, please find attached an IPSO object available for download at http://www.ipso-alliance.org/so-starter-pack/ which my colleague has modelled in YANG. Please note that the YANG model is just an example and is not approved/endorsed by IPSO or LWM2M.

Regards,
Abhinav

From: core [mailto:[e-mail]] On Behalf Of Andy Bierman
Sent: Donnerstag, 21. April 2016 23:50
To: Juergen Schoenwaelder <[e-mail]>; Michel Veillette <[e-mail]>; Hannes Tschofenig <[e-mail]>; [e-mail] WG <[e-mail]>
Subject: Re: [core] ? WG adoption of draft-veillette-core-yang-cbor-mapping-00



On Thu, Apr 21, 2016 at 2:37 PM, Juergen Schoenwaelder <[e-mail]<mailto:[e-mail]>> wrote:
On Thu, Apr 21, 2016 at 09:00:29PM +0000, Michel Veillette wrote:
> Hi Juergen
>
> The extract I have provided is from a publically available document, see:
> https://www.iab.org/wp-content/IAB-uploads/2016/03/ipso-paper.pdf
>
> My remark about the LWM2M modeling language was just to highlight that such language don't necessary imply code generation.
>

YANG does not imply code generation either. A YANG module defines a
contract, and in the light of a protocol a programmatic interface.
There is nothing in YANG that requires code generation.

It just happens that people often tend to automate things if they find
themself repeatedly writing similar code. It is at the end a question
of how much data a device exposes and what kind of developers you are
dealing with and whether you have a product that is expected to evolve
over years or something designed to be sold and thrown away
afterwards. ;-)

/js

PS: I have just implemented a YANG data model 'manually' because I had
    reasons to not depend on tool chains (the target environment are
    OpenWrt type of devices). But still I took advantage of having
    YANG tools available to validate test cases so that I can be
    reasonably sure my manually written code is a good match of the
    contract.


There are commercial and open-source toolchains that handle the NETCONF/YANG
interaction model and most of the data model details in the protocol stack, instead of pushing that
work out to the model instrumentation.  This can save a lot of code and makes sure
the client or server has consistent behavior.

But you are making an important point.
The expected use CoMI/CoOL co-authors have discussed is client firmware written
to work with specific YANG modules/revisions.  The client needs to retrieve enough
server state to know if the server supports the same module revisions, and then just assumes
the API contract will be followed.  It does not need any YANG parser or code automation.


--
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
Fax:   [phone]         <http://www.jacobs-university.de/>


Andy

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