Before revision: Given an orthogonal polygon with orthogonal holes, we devise a dynamic algorithm for guarding with vertex guards\cal \cal  , i.e., whenever orthogonal polygon is modified,\cal \cal  algorithm updates the set of vertex guards and their positions for guarding the modified orthogonal polygon\cal \cal  .
After revision: Given an orthogonal polygon with orthogonal holes, we devise a dynamic algorithm for guarding with vertex guards\cal P by placing one guard at each vertex in a subset of vertices of\cal , i.e., whenever orthogonal polygon is modified,\cal \cal algorithm updates the set of vertex guards and their positions for guarding the modified orthogonal polygon\cal \cal .