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15
Approximate Hotlink Assignment
, 2001
"... Consider a directed rooted tree T = (V, E) of maximal degree d representing a collection V of web pages connected via a set E of links all reachable from a source home page, represented by the root of T . Each leaf web page carries a weight representative of the frequency with which it is visited. B ..."
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Cited by 14 (5 self)
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Consider a directed rooted tree T = (V, E) of maximal degree d representing a collection V of web pages connected via a set E of links all reachable from a source home page, represented by the root of T . Each leaf web page carries a weight representative of the frequency with which it is visited. By adding hotlinks, shortcuts from a node to one of its descendents, we are interested in minimizing the expected number of steps needed to visit the leaf pages from the home page. We give an O(N²) time algorithm for assigning hotlinks so that the expected number of steps to reach the leaves from the root of the tree is at most H(p) log(d+1) (d=(d+1)) log d + d+1 d , where H(p) is the entropy of the probability (frequency) distribution p = on the N leaves of the given tree, i.e., p i is the weight on the ith leaf. The best known lower bound for this problem is H(p) log(d+1) . Thus our algorithm approximates the optimal hotlink assignment to within a constant for any fixed d.
Evaluation of Hotlink Assignment Heuristics for Improving Web Access
, 2001
"... We study the optimal hotlink assignment problem. Consider a web site as a directed graph, where each page is represented by a node and each link is represented by an edge. The resulting graph is connected and may have cycles. It was previously proven that the hotlink assignment problem is NPhard in ..."
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Cited by 11 (4 self)
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We study the optimal hotlink assignment problem. Consider a web site as a directed graph, where each page is represented by a node and each link is represented by an edge. The resulting graph is connected and may have cycles. It was previously proven that the hotlink assignment problem is NPhard in its full generality. We describe a way of constructing a tree that maintains the original semantic relationship between the pages of a web site. We then proceed to describe three algorithms that improve access in web site trees. We simulate our algorithms in three dierent, but closely related, kinds of trees: powerlaw trees, realistic trees, and an actual tree. These algorithms are capable of obtaining considerable savings on the access cost of the web site.
Asymmetric Communication Protocols via Hotlink Assignments
, 2002
"... We exhibit a relationship between the asymmetric communication problem of Adler and Maggs (1998) and the hotlink assignment problem of Bose et al (2000). By generalizing previous results on the hotlink problem and then exploiting this relationship we present a new asymmetric communication protoc ..."
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Cited by 10 (1 self)
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We exhibit a relationship between the asymmetric communication problem of Adler and Maggs (1998) and the hotlink assignment problem of Bose et al (2000). By generalizing previous results on the hotlink problem and then exploiting this relationship we present a new asymmetric communication protocol with different performance bounds than previous protocols.
Enhancing Hyperlink Structure for Improving Web Performance
, 2003
"... In a Web site, each page v has a probability... ..."
Multiple Hotlink Assignment
 In 27th Int. Workshop on GraphTheoric Concepts in Computer Science, volume 2204 of LNCS
, 2001
"... The input for the hotlink assignment problem consists of a node weighted directed acyclic graph with a designated root node r. The goal is to minimize the weighted shortest path length rooted at r by adding a restricted number of outgoing arcs (hotlinks) to each node. ..."
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Cited by 8 (0 self)
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The input for the hotlink assignment problem consists of a node weighted directed acyclic graph with a designated root node r. The goal is to minimize the weighted shortest path length rooted at r by adding a restricted number of outgoing arcs (hotlinks) to each node.
Hotlink enhancement algorithms for web directories
 In Proc. 14th Ann. Int. Symp. on Algorithms and Computation, volume 2906 of LNCS
, 2003
"... Abstract. Consider a web site containing a collection of web pages with data. Each page is associated with a weight representing the frequency that page is accessed by users. In the tree hierarchy representation, accessing each page requires the user to travel along the path leading to it from the r ..."
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Cited by 5 (1 self)
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Abstract. Consider a web site containing a collection of web pages with data. Each page is associated with a weight representing the frequency that page is accessed by users. In the tree hierarchy representation, accessing each page requires the user to travel along the path leading to it from the root. By enhancing the index tree with additional edges (hotlinks) one may reduce the access cost of the system. That is, the hotlinks reduce the expected number of steps needed to reach a leaf page from the tree root, assuming that the user knows which hotlinks to take. The hotlink enhancement problem involves finding a set of hotlinks minimizing this cost. The paper proposes a hotlinks structure allowing a user with limited apriori knowledge to determine which hotlink to use at every given point. Then, a polynomial algorithm is presented for solving the hotlink enhancement problem for such hotlinks on trees of logarithmic depth. The solution is first presented for binary trees and then extended to arbitrary degree trees. It is also shown how to generalize the solution to situations where more than one hotlink per node is allowed. The case in which the distribution on the leaves is unknown is discussed as well, and is given an algorithm guaranteeing (an optimal) logarithmic upper bound on the expected number of steps down the tree. 1
Optimal website design with the constrained subtree selection problem
 IN 31ST INTERN. COLLOQUIUM ON AUTOMATA, LANGUAGES, AND PROGRAMMING (ICALP
, 2004
"... We introduce the Constrained Subtree Selection (CSS) problem as a model for the optimal design of websites. Given a hierarchy of topics represented as a DAG G and a probability distribution over the topics, we select a subtree of the transitive closure of G which minimizes the expected path cost. ..."
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Cited by 4 (0 self)
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We introduce the Constrained Subtree Selection (CSS) problem as a model for the optimal design of websites. Given a hierarchy of topics represented as a DAG G and a probability distribution over the topics, we select a subtree of the transitive closure of G which minimizes the expected path cost. We define path cost as the sum of the page costs along a path from the root to a leaf. Page cost, γ, is a function of the number of links on a page. We give a sufficient condition for γ which makes CSS NPComplete. This result holds even for the uniform probability distribution. We give a polynomial time algorithm for instances of CSS where G does not constrain the choice of subtrees and γ favors pages with at most k links. We show that CSS remains NPHard for constant degree DAGs, but also provide an O(log(k)γ(d + 1)) approximation for any G with maximum degree d, provided that γ favors pages with at most k links. We also give a complete characterization of the optimal trees for two special cases: (1) linear degree cost in unconstrained graphs and
Optimal Assignment of Bookmarks to Web Pages
 In progress
"... Consider a web domain consisting of a collection V = fv 1 ; :::; vn g of web pages connected by hyperlinks. Assume that there exists a directed path of hyperlinks from the home page r to any other page of the collection. Let p i be the probability that a user wants to access page v i . ..."
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Cited by 3 (3 self)
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Consider a web domain consisting of a collection V = fv 1 ; :::; vn g of web pages connected by hyperlinks. Assume that there exists a directed path of hyperlinks from the home page r to any other page of the collection. Let p i be the probability that a user wants to access page v i .
Quicklink Selection for Navigational Query Results
"... Quicklinks for a website are navigational shortcuts displayed below the website homepage on a search results page, and that let the users directly jump to selected points inside the website. Since the realestate on a search results page is constrained and valuable, picking the best set of quicklink ..."
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Cited by 3 (0 self)
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Quicklinks for a website are navigational shortcuts displayed below the website homepage on a search results page, and that let the users directly jump to selected points inside the website. Since the realestate on a search results page is constrained and valuable, picking the best set of quicklinks to maximize the benefits for a majority of the users becomes an important problem for search engines. Using user browsing trails obtained from browser toolbars, and a simple probabilistic model, we formulate the quicklink selection problem as a combinatorial optimizaton problem. We first demonstrate the hardness of the objective, and then propose an algorithm that is provably within a factor of (1 − 1/e) of the optimal. We also propose a different algorithm that works on trees and that can find the optimal solution; unlike the previous algorithm, this algorithm can incorporate natural constraints on the set of chosen quicklinks. The efficacy of our methods is demonstrated via empirical results on both a manually labeled set of websites and a set for which quicklink clickthrough rates for several webpages were obtained from a realworld search engine.
Nearentropy hotlink assignments
 In Proceedings of the 14th Annual European Symposium on Algorithms (ESA
, 2006
"... Abstract. Consider a rooted tree T of arbitrary maximum degree d representing a collection of n web pages connected via a set of links, all reachable from a source home page represented by the root of T. Each web page i carries a weight wi representative of the frequency with which it is visited. By ..."
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Cited by 1 (0 self)
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Abstract. Consider a rooted tree T of arbitrary maximum degree d representing a collection of n web pages connected via a set of links, all reachable from a source home page represented by the root of T. Each web page i carries a weight wi representative of the frequency with which it is visited. By adding hotlinks — shortcuts from a node to one of its descendents — we wish to minimize the expected number of steps l needed to visit pages from the home page, expressed as a function of the entropy H(p) of the access probabilities p. This paper introduces several new strategies for effectively assigning hotlinks in a tree. For assigning exactly one hotlink per node, our method guarantees an upper bound on l of 1.141H(p)+1 if d> 2 and 1.08H(p)+2/3 if d = 2. We also present the first efficient general methods for assigning at most k hotlinks per node in trees of arbitrary maximum degree, achieving bounds on l of at most