The latter proposes the new work item to ISO as a whole. Once the need for an International Standard has been recognized and formally agreed, the first phase involves definition of the technical scope of the future standard. This phase is usually carried out in working groups which comprise technical experts from countries interested in the subject matter. Once agreement has been reached on which technical aspects are to be covered in the standard, a second phase is entered during which countries negotiate the detailed specifications within the standard. This is the consensus-building phase.
Most standards require periodic revision.
To take account of these factors, ISO has established the general rule that all ISO standards should be reviewed at intervals of not more than five years. On occasion, it is necessary to revise a standard earlier. ISO makes use of information technology and programme management methods. It may specify the tasks that a certain range of equipment must be able to perform, or describe in detail an apparatus and its safety features. It may contain symbols, definitions, diagrams, codes, test methods, etc.