Hub and Authority Model

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Many researchers have studied the hub/authority model. This model suggests that for any topic, there is a set of authority pages and a set of hub pages. Authority pages are those that contain credible and relevant information on a given topic, whereas hub pages contain links to authority pages. Authority is conferred based on the linkage among Web sites. When the creator of page p includes a link to page q, the creator of p has conferred authority on q (see Figure 1) (Kleinberg, 1999).

Figure 1: An illustrative example of the hub and authority model

Hubs and authorities can be discovered by measuring the relationship between their in- and out-degrees. The out-degree of p is the number of sites to which it links, and the in-degree refers to the number sites that have links to it. Out-degree pages that are significantly above average are referred to as index pages, and in-degrees that are significantly above the average are referred to as reference pages.

The hub and authority model exhibits a mutually reinforcing relationship; a good hub is a page that points to many authorities, and an authority is a page that is pointed to by many hubs (Kleinberg, 1999). Quite often the relationship among hubs and authorities exhibits a hyperlinked community. A hyperlinked community is one that contains a core central page (authority) linked together by hub pages (Gibson & Kleinberg, 1998). In summary, authorities are created by endorsements of many hub pages, and good hubs increase the authority weight or index score. In the next section, the author takes a local approach to imposing structure to the Web by developing a planned approach to the creation of a cyber-community.

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