The basic principles of IMO Goal-Based Standards are: broad, over-arching safety, environmental and/or security standards that ships are required to meet during their lifecycle; the required level to be achieved by the requirements applied by class societies and other recognized organizations, Administrations and IMO; clear, demonstrable, verifiable, long standing, implementable and achievable, irrespective of ship design and technology; and specific enough in order not to be open to differing interpretations. MSC 81 (May 2006) agreed to limit the scope of the GBS work initially to bulk carriers and oil tankers and consider expansion to other ship types and areas of safety at a later time. For the GBS for bulk carriers and oil tankers, a five-tier system was agreed and consists of the following: Tier I - Goals - High-level objectives to be met. Tier II - Functional requirements - Criteria to be satisfied in order to conform to the goals. Tier III - Verification of conformity - Procedures for verifying that the rules and regulations for ship design and construction conform to the goals and functional requirements. Tier IV - Rules and regulations for ship design and construction - Detailed requirements developed by IMO, national Administrations and/or recognized organizations and applied by national Administrations and/or recognized organizations acting on their behalf to the design and construction of a ship in order to conform to the goals and functional requirements. Tier V - Industry practices and standards - Industry standards, codes of practice and safety and quality systems for shipbuilding, ship operation, maintenance, training, manning, etc., which may be incorporated into, or referenced in, the rules and regulations for the design and construction of a ship.