The first study is an article by John J. Contreni entitled "The Carolingian School: Letters from the Classroom."  While Contreni did not explicitly set out to reconstruct an intellectual network, his piece is useful for our purposes because of the wide selection of scholars featured in it. From the intellectual scene Contreni sketches, networks emerge.
Diagram 1, constructed using Wordle, serves to introduce the more than forty individuals whose connections are discussed in Contreni's paper. By counting the number of times each individual's name occurs in Contreni's text, I was able to produce a word cloud that provides a sense of the relative influence and importance of each intellectual, at least for Contreni. This representation of Contreni's "network" gives an impression of the size of the scholarly crowd, but is most useful for identifying those individuals within it that loom largest in his study: Lupus, Ermenric, Alcuin, Hrabanus, and John Scottus.
Two of these names—John Scottus and Ermenric—achieve prominence by the accident of Contreni's argument, as it were. Contreni's article was first published in the proceedings of a conference devoted to the Carolingian philosopher John Scottus, which explains the relatively high number of references to this important scholar. These references to John Scottus are almost entirely confined to the opening and closing paragraphs of Contreni's article, however. They belong merely to the frame and not the main picture. We know so little about the where and when of John Scottus that it is almost impossible to connect him with any other known Carolingian intellectual. Ermenric is another matter. A monk originally from the monastery of Ellwangen, he is perhaps most famous for one long and rather eccentric letter.  Contreni's discussion of the letter over several pages of his article is the reason Ermenric's name has made it into the top five. If we filter out John Scottus and Ermenric we are left with three names:
- Lupus (c. 805-862), a monk and later abbot of the monastery of Ferrières in north-central France;
- Alcuin (†804), an Anglo-Saxon cleric, and one of the most famous and important scholars and teachers of the Carolingian age. He became an adviser to Charlemagne, a teacher at his court, and later abbot of the monastery of Tours.
- Hrabanus (c.780-856), a monk at, and then abbot of the monastery of Fulda on the eastern edge of the Carolingian Empire. He was later elected to the archbishopric of Mainz.
These three men are, to medievalists, the "usual suspects" when we talk about scholarship and education in the Carolingian Renaissance. Their prominence in the Wordle diagram of Contreni's article is not surprising.
Diagram 2, created using Gephi, an open-source visualization platform, better illustrates emergent networks in Contreni's piece. It shows more clearly how Lupus, Alcuin and Hrabanus achieved their prominence in the word cloud. Diagram 2 is based purely on the letters used by Contreni to explore relationships between scholars. Each edge in the diagram represents a letter.
Visualizing Contreni's data in this way is interesting because it suggests relative sizes of network: Lupus enjoys the largest, then Alcuin, then Hrabanus. It is also striking that these three scholars and their networks appear not to intersect with each other, or with anyone else featured in the diagram. A curious result because, as every historian of the early middle ages—and certainly Contreni—knows, Alcuin taught Hrabanus who in turn taught Lupus, yet these particular connections aren't evidenced in the letters selected by Contreni for his article. Instead, when we visualize Contreni's data, separate egocentric networks emerge around each letter writer. This, I would argue, is typical of the way historians tend to approach early medieval networks. The reality is far more complex.
I will return to the problem of selectivity in text-based network studies later. First, let us consider two important factors that tend to get taken for granted, downplayed, or even overlooked in network studies: the location of the individuals in question, and the dates when they were active.