4.27. The safety strategy refers to the approach that will be taken in site selection and facility design to comply with the safety objectives, principles and criteria, to comply with regulatory requirements and to ensure that good engineering practice has been adopted and that safety and protection are optimized. The strategy should be established at the early stage of conceptualization of the disposal facility. In the early stages, the strategy may develop and mature, but it should be defined at as early a stage as possible. By the time the site is selected, the design concept to implement the strategy should be sufficiently well developed to provide assurance that the overall disposal system will provide and preserve the safety functions envisaged for the disposal facility. As the project develops, the safety strategy should be continually validated and any changes to it should be justified in the safety case. Any evolution of the safety strategy should be carefully recorded and the records should be preserved for use in the future when staff may have changed.