Before revision:   * Answering visibility polygon query corresponding to any point located exterior to simple polygon amid vertex insertions and deletions to  simple polygon.
After revision:  The time complexity to update the visibility polygon of a point q due to the insertion (resp. deletion) of vertex v to (resp. from) the current simple polygon is expressed in terms of the number of combinatorial changes needed to the visibility polygon of q due to the insertion (resp. deletion) of v. * Answering visibility polygon query corresponding to any point located exterior to simple polygon amid vertex insertions and deletions to simple polygon.