Impact of URI Canonicalization on Memento Count

Memento TimeMaps list identifiers for archival web captures (URI-Ms). When some URI-Ms are dereferenced, they redirect to a different URI-M instead of a unique representation at the datetime. This suggests that confidently obtaining an accurate count quantifying the number of non-forwarding captures for an Original Resource URI (URI-R) is not possible using a TimeMap alone and that the magnitude of a TimeMap is not equivalent to the number of representations it identifies. This work represents an abbreviated version of the full technical report describing this phenomena in depth. For google.com we found that 84.9% of the URI-Ms in a TimeMap result in an HTTP redirect when dereferenced. The full study applies this technique to seven other URI-Rs of large Web sites and 13 academic institutions. Using a ratio metric for the number of URI-Ms without redirects to those requiring a redirect when dereferenced, five of the eight large web sites' and two of the thirteen academic institutions' TimeMaps had a ratio of less than one, indicating that more than half of the URI-Ms in these TimeMaps result in redirects when dereferenced.