Coherence-Oriented Crawling and Navigation Using Patterns for Web Archives

We point out, in this paper, the issue of improving the coherence of web archives under limited resources (e.g. bandwidth, storage space, etc.). Coherence measures how much a collection of archived pages versions reflects the real state (or the snapshot) of a set of related web pages at different points in time. An ideal approach to preserve the coherence of archives is to prevent pages content from changing during the crawl of a complete collection. However, this is practically infeasible because web sites are autonomous and dynamic. We propose two solutions: a priori and a posteriori. As a priori solution, our idea is to crawl sites during the off-peak hours (i.e. the periods of time where very little changes is expected on the pages) based on patterns. A pattern models the behavior of the importance of pages changes during a period of time. As an a posteriori solution, based on the same patterns, we introduce a novel navigation approach that enables users to browse the most coherent page versions at a given query time.