Exploring the academic invisible web

Purpose - The purpose of this article is to provide a critical review of Bergman's study on the deep web. In addition, this study brings a new concept into the discussion, the academic invisible web (AM. The paper defines the academic invisible web as consisting of all databases and collections relevant to academia but not searchable by the general-purpose internet search engines. Indexing this part of the invisible web is central to scientific search engines. This paper provides an over-view of approaches followed thus far. Design/methodology/approach - Provides a discussion of measures and calculations, estimation based on informetric laws. Also gives a literature review on approaches for uncovering information from the invisible web. Findings - Bergman's size estimate of the invisible web is highly questionable. This paper demonstrates some major errors in the conceptual design of the Bergman paper. A new (raw) size estimate is given. Research limitations/implications - The precision of this estimate is limited due to a small sample size and lack of reliable data. Practical implications - This study can show that no single library alone will be able to index the academic invisible web. The study suggests a collaboration to accomplish this task. Originality/value - Provides library managers and those interested in developing academic search engines with data on the size and attributes of the academic invisible web.