The principal long-term guide for improving the TWS. The Plan provides a summary of the basic elements which comprise the TWS, a description of its existing components, and an outline of the activities, data sets, methods, and procedures that need to be improved in order to reduce tsunami risk. The first edition of the ICG/PTWS Master Plan was released in 1989. The third edition was released in 2004 (IOC/INF-1124 Rev). (http://www.unesco.org/ulis/cgi-bin/ulis.pl?catno=117788&set=50C4D77D_0_77&gp=1&lin=1&ll=1)