The protypical Linked Open Data map gives the general impression of a richly interlinked set of bubbles.However, A small experiment showed that this first impression is very wrong! Christophe Gueret from the VU Amsterdam re-constructed the LOD link table as a .net file, which we then displayed using simple stress minimisation in Visione. This revealed some surprises:
(click on image for bigger copy)
Surprise 1: There is not one cloud, but three. As this graph visualisation shows, LOD is not one cloud, but three, each with dense internal connections and only sparse connections between them. The three sub-clouds are also clearly recognisable: one sub-cloud is bio/life-sciences data, one sub-cloud is (surprisingly) academic bibliographic material, and the central cloud is “all the rest”, connecting the other two, with DBPedia as its hub.
Surprise 2. DBLP is as important as DBPedia. Also surprisingly, the total betweenness degree of the relatively unknown DBLP datasets is as high as the betweenness degree of the widely recognised DBPedia hub. The sum of three DBLP instances accounts for 25% of the betweenness, almost the same number as DBPedia (28%). The reason for this high betweenness is that the DBLP sets are the only link between the bibliographic subcloud and “the rest”.
So now the questions are: Is this good or bad? Is this surprising or obvious? Is this long-term structural or just a short-term coincidence. Anybody?(a first experiment would be to take the density of the links between the bubbles into account, and see if this would change anything? The .net file is here for you to experiment with, please share your results).