About items not in the document

In the document (https://github.com/blockchain-certificates/cert-schema/blob/master/docs/schema-2.md), “SignatureLine”, “RecipientProfile”, “MerkleProof2017” etc. are “undefined” and details are unknown is. Is there any documentation about this?
Also, Learning-machine’s sample JSON has “nonce” and “universalIdentifier” items, which are also missing from the documentation. Is it your own extension item? .

That schema was created with a json to markdown tool which isn’t always perfect in detecting certain details - displays undefined sometimes. You can find the documentation inside of the json files themselves https://github.com/blockchain-certificates/cert-schema/tree/master/cert_schema/2.0

And yes, you can view the contexts of some of the learning machine sample json files and see that additional fields are sometimes added.