Dear UBL Committee
Tradeshift is happy to see the formalization of an JSON alternative UBL representation in form of JSON (draft-04) Schemas . We are in the process of aligning our own JSON representations to match these. In that process, we have tried to perform JSON schema validation using the schemas published here 
I have the following comments:
1: The "common" and "maindoc" JSON schemas are lacking the $id property,
From the spec:
"The "$id" keyword defines a URI for the schema, and the base URI that other URI references within the schema are resolved against. The "$id" keyword itself is resolved against the base URI that the object as a whole appears in."
So if e.g. the "UBL-Invoice-2.1.json" would define
and the "UBL-CommonBasicComponents-2.1" would define
Then references should be written like
Which is much cleaner IMHO than the relative path solution, which also is not a valid URI e.g. "../common/", and also to my knowledge how most tools work.
2: Any plan for updating the schema version to the final version?
3: The DateType in UBL-UnqualifiedDataTypes-2.1.json is defined as
I believe that to be contradicting since "date-time" is "full-date "T" full-time" , that cannot coexist with the regex pattern as well.
I have been unable to find any previous discussion of this, please bear with me if this has been discussed before.
I have uploaded a ZIP file containing a small node script that can do validation of an invoice. Also an upgraded version of the JSON schemas to version 6 is included.
Thank you for your consideration.