One more query related to revision of schema sources
#1 right now ODL does not support scheam sources without revision.
which leads to Bug in Yang specification and ODL

already commented on CONTROLLER-641
Regarding this bug, there is plenty of evidence in RFC 6020 that the first revision of a YANG module does not need to have a "revision" statement, and hence not needed in the <hello> message, but section 5.6.4.1 says:

"A server MUST advertise all revisions of all modules it implements."

Which seems contradictory. Discussing with the NETMOD WG, it is agreed that the sentence should have been written:

"A server MUST advertise all known revisions of all modules it implements."

Thus providing the necessary leeway.

FWIW, the only time it is envisioned a YANG module not wanting to have an initial revision date is when the module itself is already version-specific (e.g., http://xml.juniper.net/netconf/junos/14.2R2.4), which clearly will have one and only one revision. In all other cases, it seems the module is expected to be versioned over time and therefore SHOULD have a revision statement. For this reason, the NETMOD WG may also add a clarifying statement into section 7.1.9.