Link awareness is defined as the ability to discover, view, search and update global hyperlink

Hyperlink

In computing, a hyperlink is a reference to data that the reader can directly follow, or that is followed automatically. A hyperlink points to a whole document or to a specific element within a document. Hypertext is text with hyperlinks...

 information about any resource with a URL

Uniform Resource Locator

In computing, a uniform resource locator or universal resource locator is a specific character string that constitutes a reference to an Internet resource....

 on the World Wide Web

World Wide Web

The World Wide Web is a system of interlinked hypertext documents accessed via the Internet...

. This global link information is a shared information resource.

Implementing link awareness is difficult. In practice, an implementation only approximates link awareness. There are at least two qualitative axes on which we can classify these implementations.

• Breadth of Coverage: The number and type of interlinked documents covered.
• Liveness: The ability (or lack thereof) to update the link information on the fly.

Implementation examples

• Most WikiWiki implementations support link awareness within the scope of the documents that they host. Their breadth of coverage (insofar as link information is concerned) is narrow. A wiki, however, is very live (and indeed, liveness, is its raison d'etre).
• Google
  Google search
  Google or Google Web Search is a web search engine owned by Google Inc. Google Search is the most-used search engine on the World Wide Web, receiving several hundred million queries each day through its various services....
  
  supports link awareness through its web interface. (You type in a query of the form link:<URL>.) Google's breadth is impressive (it covers a lot of interlinked documents), but it is a far cry from live (it can take months before Google indexes a newly created document).

Related Reading

• Structural Analysis of the World Wide Web, Gibson, Kleinberg, Raghavan
• Surfing the Web Backwards, Chakrabarti, Gibson, McCurley.