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Validating a JSON fragment against YANG

Problem: we want to know whether a piece of JSON is compliant with a YANG model without using a client/server.

The wrong way (XSD-based)

This did not work. It is reported just to save your time.

The idea is to convert YANG to XSD, JSON to XML and validate it against the XSD.

            (1) 
YANG-module ---> XSD-schema - \       (3)
                               +--> Validation
JSON-file------> XML-file ----/
            (2)

pyang support for the XSD output format was deprecated in 1.5 and removed in 1.7.1. 1.7.1 is necessary to work with YANG 1.1 so the process stops just at (1).

The right way (DSDL-based)

The steps are outlined below:

  1. The driver file (JTOX) is generated from the YANG module. It is a JSON describing the YANG module.
  2. An XML file is generated from the input JSON and the driver file and an option (either config or data). Warning: check whether this means that rpc and notifications are not supported.
  3. The DSDL schemas for a given target are generated from the YANG module. target is the target document, i.e. one of data, config, get-reply, rpc etc.
  4. The XML document generated in step 2. is validated against the schemas.

Useful link: https://github.com/mbj4668/pyang/wiki/XmlJson

           data|config|rpc|rpc-reply|etc..
                      \
                       \
                        \ (3) 
         YANG-module ----+----> DSDL-schemas (RNG,SCH,DSRL)
                |                  |
                + (1)              |
                |                  | 
config|data  JTOX-file             |
       \        |                  |
        \       |                  |
         \      V                  V
JSON-file------>+----> XML-file -->+------------> Output
               (2)                (4)

Prerequisites: YANG tools and jing to have more useful output in case of failed XML validation. If you do not want to use jing, remove the -j from the yang2dsdl in step (4).

How to run examples

In this directory you should see two files clean_examples and run_examples and a directory (guess?) example. Run run_example to run all the examples.