This is the final blog in a series of guest blog posts by Robyn Adams and Jaap Geraerts, part of the project team that won the DM2E Open Humanities Award at the Center for Editing Lives and Letters. The final report is available here.

The blind spots of network visualizations

In our last blog we discussed some of the issues regarding the use of network visualizations as well as the limits of the information such visualizations might convey. We will examine this topic into more detail in this blog by employing some of the data derived from our own project. To reiterate a point we previously made, network visualizations often include only one type of relationship, which obscures the various links which connected people to one another. When analysing epistolary networks and the dissemination of information, the omission of such links can be of vital importance, for even when letters were sent to one person, often recipients were asked to pass on information to a third party. Often letters were packages, consisting of multiple letters or including other documents that sometimes were addressed to different people, thus turning a recipient (or the first recipient of the package) into a transmission agent, a person responsible for dispatching the documents or the information to their final destination. Besides the fact that people had different roles, how can we include the flow of information that resulted from people meeting in person to convey the information they received via letters, for instance?

We will illustrate the limits of a visualization of a binary epistolary network by focussing on a case-study, namely the correspondence and the transmission of information regarding the siege of Groningen, which took place in the late-spring and summer of 1594. The following image is a traditional network visualization, the edges representing the letters sent between Bodley and his correspondents regarding the siege of Groningen in the period May to August 1594.¹

This simple visualization tells us, for instance, that only a small number of people wrote about the siege and that Bodley was the main correspondent, yet there is much more information that is not represented in or by this image. The visualization also creates the impression that, while the siege was of great importance to the Dutch authorities, it nevertheless was only discussed by English correspondents who were part of the epistolary network. In order to show which people actually were involved in transmitting information, the way in which they did this, and the various links that were forged in the process of disseminating information about the siege, we returned to the primary sources. Extra research was necessary as we wanted to move beyond the basic relationship codified in our dataset, namely the authors and recipients of the letters, to include a large palette of connections which linked people to one another. The results are visualized in a SDL-diagram, which is normally used to depict processes within a particular system (e.g. a computer program), yet its format enabled us to track the flow of the information as well as the various actions and the ensuing relationships. The diagram follows after the figure below, which is a key to the symbols used.

Because of the density of the information included in the diagram, it might be initially more challenging to ‘read’ the image, but it immediately becomes apparent that a lot more people were involved in the exchange of information regarding the siege than has been shown in the network visualization, including the Dutch stadholder, Maurice of Orange, and Sir Francis Vere. Other relationships are also visible: in her letter to Bodley (letter id. 29), Queen Elizabeth asked him to convey the Queen’s message to the Council of State, the Estates General, and to Maurice of Orange. It is likely that Bodley went to see the members of these political bodies in person in order to pass on the information, hence links were created that existed outside of but are closely related to the epistolary network.

The diagram makes it clear that Bodley was not ‘just’ a correspondent, but also acted as a transmission agent, and the people who normally took care of transporting the letters, the bearers, can be easily included in the diagram as well (thus expanding the network and more clearly showing the different people who were involved in the transmission of information and who connected the various correspondents to one another). The sources from which Bodley derived his information are also shown: on July 14, 1594, Bodley wrote to Robert Cecil (letter id. 454) about the siege and he mentioned that he had received letters from the army camp at Groningen which provided him with information. The symbols indicate where other documents were enclosed with the letters sent between the correspondents: a letter package from Bodley to Burghley included a map about the siege of Groningen, one of the three maps about the siege Bodley sent to England.²

The SDL-diagram is one way of including various types of relationships and different flows of information that are difficult to include in many network visualizations (when using open source visualization software). Instead of depicting straightforward binary networks consisting of authors and recipients, we can zoom in closer, as it were, and show the material processes of collecting and disseminating information in more detail. Moreover, using such visualizations enables us to capture the complexity of the historical data as well as the diversity of the network. Arguably this comes at the cost, for it is difficult to visualize a large dataset in this way, but it opens up possibilities of visualizing networks without losing too much of the complexity and richness of the historical data which makes it so interesting to study in the first place. It also enhances our understanding of the often idiosyncratic process of gathering and spreading information and the fluid character of early modern information networks, aspects which tend to be ill-represented in neatly constructed network visualizations.