• A Free Database of University Web Links: Data Collection Issues

      Thelwall, Mike (2003)
      This paper describes and gives access to a database of the link structures of 109 UK university and higher education college websites, as created by a specialist information science web crawler in June and July of 2001. With the increasing interest in web links by information and computer scientists this is an attempt to make available raw data for research that is not reliant upon the opaque techniques of commercial search engines. Basic tools for querying are also provided. The key issues concerning running an accurate web crawler are also discussed. Access is also given to the normally hidden crawler stop list with the aim of making the crawl process more transparent. The necessity of having such a list is discussed, with the conclusion that fully automatic crawling is not socially or empirically desirable because of the existence of database-generated areas of the web and the proliferation of the phenomenon of mirroring.This paper describes a free set of databases of the link structures of the university web sites from a selection of countries, as created by a specialist information science web crawler. With the increasing interest in web links by information and computer scientists this is an attempt to make available raw data for research that is not reliant upon the opaque techniques of commercial search engines. Basic tools for querying are also provided. The key issues concerning running an accurate web crawler are also discussed. Access is also given to the normally hidden crawler stop list with the aim of making the crawl process more transparent. The necessity of having such a list is discussed, with the conclusion that fully automatic crawling is not socially or empirically desirable because of the existence of database-generated areas of the web and the proliferation of the phenomenon of mirroring.
    • Methodologies for crawler based Web surveys.

      Thelwall, Mike (MCB UP Ltd, 2002)
      There have been many attempts to study the content of the Web, either through human or automatic agents. Describes five different previously used Web survey methodologies, each justifiable in its own right, but presents a simple experiment that demonstrates concrete differences between them. The concept of crawling the Web also bears further inspection, including the scope of the pages to crawl, the method used to access and index each page, and the algorithm for the identification of duplicate pages. The issues involved here will be well-known to many computer scientists but, with the increasing use of crawlers and search engines in other disciplines, they now require a public discussion in the wider research community. Concludes that any scientific attempt to crawl the Web must make available the parameters under which it is operating so that researchers can, in principle, replicate experiments or be aware of and take into account differences between methodologies. Also introduces a new hybrid random page selection methodology.