Methods for Exploiting Academic Hyperlinks Mike Thelwall Statistical Cybermetrics Research Group University of Wolverhampton, UK

The Problem To map patterns of communication between researchers in a country based upon university web sites Patterns of communication are also mapped based upon journal citations or journal title words Provides useful information about the structure and evolution of research fields Can identify previously unknown field connections Web analysis could illustrate wider and more current patterns

Data collection Web crawler AltaVista advanced queries host:wlv.ac.uk AND link:gla.ac.uk AllTheWeb advanced queries Google Does not support same level of Boolean querying

Types of link count Direct link counts Inter-site links only Co-inlink counts B and C are co-inlinked Co-outlink counts D and E are co-outlinked BC A DE F

Alternative Document Models Domain ADM Count links between domains (ignoring multiple links) instead of pages P1 P2 P3 P4 P5 P6

Alternative Document Models Directory ADM Counts links between directories Estimated using URL slashes University ADM Counts links between entire university Web sites Too extreme for most purposes ADMs reduce the impact of replicated links E.g. a subsite of 1000 pages linking to another university home page in its navigation bar

Some Inter-University Hyperlink Patterns For the UK and Europe

Citation-Style Hyperlink Analysis Citation counts are known to be reasonable indicators of research quality but is the same true for inlink counts? Counts of links to universities within a country can correlate significantly with measures of research productivity The significance of this result is in giving ‘permission’ to investigate the use of inter-university links for researching scholarly communication

Most links are only loosely related to research 90% of links between UK university sites have some connection with scholarly activity, including teaching and research But less than 1% are equivalent to citations So link counts do not measure research dissemination but are more a natural by-product of scholarly activity Cannot use link counts to assess research Can use link counts to track an aspect of communication

Links to UK universities against their research productivity The reason for the strong correlation is the quantity of Web publication, not its quality This is different to citation analysis

Universities tend to link to neighbours

Universities cluster geographically

Language is a factor in international interlinking English the dominant language for Web sites in the Western EU In a typical country, 50% of pages are in the national language(s) and 50% in English Non-English speaking extensively interlink in English {Research with Rong Tang & Liz Price}

Can map patterns of international communication Counts of links between EU universities in Swedish are represented by arrow thickness.

Counts of links between EU universities in French are represented by arrow thickness.

Which language???

Linking patterns vary enormously by discipline No evidence of a significant geographic trend Disciplinary differences in the extent of interlinking: e.g., history Web use is very low, Chemistry is very high Individual research projects can have an enormous impact upon individual departments E.g. Arts web sites are often for specific exhibitions or for digital media projects Links not frequent enough to reliably reveal patterns of interdiscipliniarity

Clustering using links

Background: Power laws in Academic Webs Academic Webs have a topology dominated by power laws, including Counts of links to pages (inlink counts) Counts of links to pages (outlink counts) Groups of interconnected pages Directed component sizes Undirected component sizes Power laws mean that clustering connected components will not yield useful results

Page Outlinks

Topological component sizes

Community Identification Algorithm Can apply to page, directory and domain models Gives complimentary results: a “layered approach”

Stretching links further: co- inlinks, co-outlinks For the UK academic Web, about 42% of domains connected by links alone host similar disciplines, and about 43% connected by links, co-inlinks and co-outlinks But over 100 times more domains are colinked or coupled than are directly linked Links in any form are less than 50% reliable as indicators of subject similarity

Summary Studies of the relatively restricted subdomain of university web sites Produce directly useful results For Web IR, they also Help refine methodologies Help build intuition