Accessibility in Information Retrieval

The other day, I was talking with Leif Azzopardi at the University of Glasgow about accessibility in information retrieval. Accessibility is a concept borrowed from land use and transportation planning: it measures the cost that people are willing to incur to reach opportunities (e.g., shopping, restaurants), weighted by the desirability of those opportunities.

What does accessibility mean in the context of information retrieval?

Instead of an actual physical space, in IR, we are predominately concerned with accessing information within a collection of documents (i.e., information space), and instead of a transportation system, we have an Information Access System (i.e., a means by which we can access the information in the collection, like a query mechanism, a browsing mechanism, etc). The accessibility of a document is indicative of the likelihood or opportunity of it being retrieved by the user in this information space given such a mechanism.

It's a very appealing way to measure the effectiveness with which the an information retrieval system exposes a document collection--as well as the bias the system imposes. While the paper offers more questions than answers, I recommend to anyone who is interested in thinking outside the box of the traditional IR performance measures.