A global map of science based on the ISI subject categories

TLDR

The decomposition of scientific literature into disciplinary and subdisciplinary structures is a core goal of scientometrics. The study seeks to determine how to achieve an effective decomposition of scientific literature. The authors aggregate the journal‑journal citation matrix from the Journal Citation Reports using ISI subject categories, producing an asymmetrical citing‑versus‑cited matrix. Exploratory factor analysis of this matrix yields a 14‑factor solution that maps the disciplinary structure of science, and the resulting nested maps are available online, indicating a comprehensive but somewhat imprecise large‑scale representation.

Abstract

Abstract The decomposition of scientific literature into disciplinary and subdisciplinary structures is one of the core goals of scientometrics. How can we achieve a good decomposition? The ISI subject categories classify journals included in the Science Citation Index (SCI). The aggregated journal‐journal citation matrix contained in the Journal Citation Reports can be aggregated on the basis of these categories. This leads to an asymmetrical matrix (citing versus cited) that is much more densely populated than the underlying matrix at the journal level. Exploratory factor analysis of the matrix of subject categories suggests a 14‐factor solution. This solution could be interpreted as the disciplinary structure of science. The nested maps of science (corresponding to 14 factors, 172 categories, and 6,164 journals) are online at http://www.leydesdorff.net/map06 . Presumably, inaccuracies in the attribution of journals to the ISI subject categories average out so that the factor analysis reveals the main structures. The mapping of science could, therefore, be comprehensive and reliable on a large scale albeit imprecise in terms of the attribution of journals to the ISI subject categories.