(a) For the purposes of this Article, confidential information shall mean any information, regardless of the medium in which it is expressed, which is
(i) in the possession of a party,
(ii) not accessible to the public,
(iii) of commercial, financial or industrial significance, and
(iv) treated as confidential by the party possessing it.
(b) A party invoking the confidentiality of any information it wishes or is required to submit in the arbitration, including to an expert appointed by the Tribunal, shall make an application to have the information classified as confidential by notice to the Tribunal, with a copy to the other party. Without disclosing the substance of the information, the party shall give in the notice the reasons for which it considers the information confidential.