2. Mapping a research field

Web of Science<sup>2</sup> does it in 3 knowledge areas (sciences, social sciences and arts and humanities)

Scopus currently has more than 70 million records and a defined group of metadata3 that are rigorously linked to each publication to describe its academic, social and geopolitical context. These two characteristics, having large volumes of structured information, are the inputs for the application of visualization techniques that generate new representations of knowledge,

The bibliometric data are very valuable to identify the scientific publications with the greatest impact in a given discipline, (i.e., Information Systems [1], Renewable Energy, Sustainability and Environment [2], to recognize different scientific fields and understand their internal dynamics and cognitive structure [3], either as an already consolidated research field or as an

There are multiple methods and tools to visualize bibliometric information. For example, the distance-based, the graph-based or the time-based [4]. Mapping and clustering are also used to analyze the research fields of a scientific domain and the relationship between research fields and the evolution of the domain over time. As a tool, VOSViewer4 assures the comprehensive visualization of nodes labels on the map. These maps, called science maps, help to locate research results to explore collaborations and publication trends, to observe the evolution of a certain subject or discipline and for benchmarking activities between regions, countries, institutions, authors and disciplines [5]. However, the visualization must have the capacity to handle large amounts of data at a small and large scale. This reduces the visual search time, providing a better understanding of a complex data set. It also reveals relationships that otherwise would not be noticed, allowing a data set to be viewed simultaneously from several perspectives, aiding the formulation of hypotheses and being an effective source of communi-

Through the overlay of science maps, the research bodies can be located visually within the sciences, analyzing the scientific development of properly established disciplines, trends or emerging research topics that do not fit into traditional subject categories. This is achieved thanks to the existence or construction of a stable corpus on which another smaller body can be overlaid [7], producing intuitive comparisons, of greater interpretation and with the potential

In its essence, science maps are matrices of similarity measures, calculated from the correlation between items of information present in the structure of scientific communication. In other words, they show the disciplinary structure of the sciences in terms of publications. The stable or base map is constructed with bibliographic data from a database that has a definite categorization of the sciences. The analysis made from the overlap will be conditioned by the size of

and 250 thematic categories.

50 Scientometrics

emerging discipline.

cation [6].

to be used in scientific analysis.

http://clarivate.com/products/journal-citation-reports/

https://www.elsevier.com/solutions/scopus/content

the data selected for it.

http://www.vosviewer.com

2

3

4

thus becoming powerful tools for science analysis.

To perform the research field mapping, we must first establish a body of documents to perform the bibliometric analysis, ensuring access to the bibliometric data of this set of publications. To analyze the e-learning case, we started with the methodology and findings of Tibaná-Herrera and others [9] for the subject categorization.

Secondly, the subject research fronts are identified, which determine the consolidation of the different tendencies over time that have contributed to the development and growth of the subject in scientific communications [16]. We propose the use of wordclouds composed of keywords [17], to visualize the research fronts of the field due to its representation capacity and rapid appropriation of the community to which it is presented.
