Mitigating the vulnerability of government and private sector operations to man-made or natural disasters depends not only on the structural resilience of our assets, systems, and networks but also on operational resilience. First, we will continue to maintain comprehensive and effective continuity programs, including those that integrate continuity of operations and continuity of government programs, to ensure the preservation of our government under the Constitution and the continuing performance of national essential functions - those government roles that are necessary to lead and sustain the Nation during and following a catastrophic emergency. A national approach to continuity also requires that State, local, and Tribal governments work to ensure that they are able to maintain or rapidly resume effective functioning during and after catastrophic incidents and are able to interact effectively with each other and the Federal Government. Likewise, we strongly encourage the private sector to conduct business continuity planning that recognizes interdependencies and complements governmental efforts - doing so not only helps secure the United States, but also makes good longterm business sense for individual companies. Such integrated and comprehensive planning is essential to protecting and preserving lives and livelihoods and maintaining our robust economy during crises. (White House, National Strategy for Homeland Security, October 2007, p. 29)