The classification process begins with the evaluation by the classification society of a submitted design to determine its compliance with the rules. During construction, classification society surveyors attend the vessel to verify that it is built in conformance with the drawings and to the rules. On delivery, the vessel will receive periodic surveys by the society to verify that it is being maintained to the required standard. These surveys generally follow a five-year cycle of annual, intermediate, and special surveys with the extent of the survey varying depending upon the age of the vessel or offshore unit and the type of survey being conducted.