On Approximation of Bookmark Assignments

Consider a rooted directed acyclic graph G = (V, E) with root r, representing a collection V of web pages connected via a set E of hyperlinks. Each node v is associated with the probability that a user wants to access the node v. The access cost is defined as the expected number of steps required to reach a node from the root r. A bookmark is an additional shortcut from r to a node of G, which may reduce the access cost. The bookmark assignment problem is to find a set of bookmarks that achieves the greatest improvement in the access cost. For the problem, the paper presents a polynomial time approximation algorithm with factor (1−1/e), and shows that there exists no polynomial time approximation algorithm with a better constant factor than (1−1/e) unless NP ⊆ DT IME(NO(log log N) ), where N is the size of the inputs.

• Type: Conference
• Year: 2007
• Where: MFCS
• Authors: Yuichi Asahiro, Eiji Miyano, Toshihide Murata, Hirotaka Ono
• Keywords: Access Cost, MFCS 2007, Node, Root R