Randomized algorithms
SPHINX: a framework for creating personal, site-specific Web crawlers
WWW7 Proceedings of the seventh international conference on World Wide Web 7
Computers and Intractability: A Guide to the Theory of NP-Completeness
Computers and Intractability: A Guide to the Theory of NP-Completeness
An O(v|v| c |E|) algoithm for finding maximum matching in general graphs
SFCS '80 Proceedings of the 21st Annual Symposium on Foundations of Computer Science
An explicit lower bound for TSP with distances one and two
STACS'99 Proceedings of the 16th annual conference on Theoretical aspects of computer science
Variable length sequencing with two lengths
APPROX '00 Proceedings of the Third International Workshop on Approximation Algorithms for Combinatorial Optimization
Approximation Algorithms for Time-Dependent Orienteering
FCT '01 Proceedings of the 13th International Symposium on Fundamentals of Computation Theory
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Web traversal robots are used to gather information periodically from large numbers of documents distributed throughout the Web. In this paper we study the issues involved in the design of algorithms for performing information gathering of this kind more efficiently, by taking advantage of anticipated variations in access times in different regions at different times of the day or week. We report and comment on a number of experiments showing a complex pattern in the access times as a function of the time of the day. We look at the problem theoretically, as a generalisation of single processor sequencing with release times and deadlines, in which performance times (lengths) of the tasks can change in time. The new problem is called Variable Length Sequencing Problem (VLSP). We show that although the decision version of VLSP seems to be intractable in the general case, it can be solved optimally for lengths 1 and 2. This result opens the possibility of practicable algorithms to schedule searches efficiently when expected access times can be categorised as either slow or fast. Some algorithms for more general cases are examined and complexity results derived.