definiens: means any challenge in a legal or administrative proceeding to thepatentability, validity or enforceability of any of the Nogra Patent Rights ( or any claim thereof ), includingby : ( a ) filing or pursuing a declaratory judgment action in which any of the Nogra Patent Rights is allegedto be invalid or unenforceable ; ( b ) citing prior art against any of the Nogra Patent Rights ( other than artrequired to be cited under a duty of candor to a patent office ), filing a request for or pursuing a re - examination of any of the Nogra Patent Rights ( other than with Nogra ’s written agreement ), or becominga party to or pursuing an interference ; or ( c ) filing or pursuing any re - examination, opposition, cancellation, nullity or other like proceedings against any of the Nogra Patent Rights ; but excluding any challengeraised as a defense against a claim, action or proceeding asserted by Nogra or its Affiliates againstLicensee or its Affiliates or Sublicensees