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Observation of changing information sources.

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Call No.	T58.64 .B74 2000
Author	Brewington, Brian E.
Title	Observation of changing information sources.
Date	2000
Abstract	Many modern information management tasks consist of an observer that must maintain current knowledge of a collection of changing information. The goal of this observer is to maintain acceptably accurate state estimates given limited observation resources, such as bandwidth, time, and storage. Good examples of such observation problems are found in any situation where bandwidth is limited and old observations become less useful over time. Two such examples are maintaining a search engine''s index of the World Wide Web (WWW) and automated monitoring of multiple sensors. This thesis addresses the general observation problem by (1) devising a formal framework of what it means to be "up-to-date", (2) gathering empirical data about the web that allows us to apply this framework to an important setting, and (3) presenting algorithms for scheduling revisits to optimize formal performance measures. One year's worth of web page observations are analyzed to show how quickly and in what ways web pages change. The observations are used to estimate the distribution of web page change rates. Using this data as a model of the web we present and benchmark an algorithm for optimizing the observation of a set of web documents such that fewer changes go unnoticed. Our experiments on real search engines show that between 40 and 50% of results returned have been altered at least once since the search engine last observed them. Our algorithm can theoretically reduce these figures to between 36 and 44%, assuming that existing search engines currently use simple round-robin re-indexing strategies. These methods benefit the "overworked" observer much more than the one with ample bandwidth, and are general enough to be of use in a wide variety of monitoring tasks.
Description	1 online resource (x, 145 leaves) : illustrations
Format	application/pdf
Advisor	Cybenko, George V.
Subject	Information resources management -- Mathematical models. ; Database management -- Methodology. ; Change. ; World Wide Web.
College	Thayer School of Engineering.
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D)--Dartmouth College.
Copyright	In Copyright. This material is protected by copyright and/or related rights. You are free to use this material in any way that is permitted by copyright law that applies to your use. For other uses, you need to obtain permission from the rights-holder(s). http://rightsstatements.org/page/InC/1.0/
DOI	https://doi.org/10.1349/ddlp.2673

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Observation of changing information sources.

Observation of changing information sources.