Designing Data-Intensive Applications: The Big Ideas Behind Reliable, Scalable, and Maintainable Systems

by Martin Kleppmann

By using different labels for different kinds of relationships, you can store several different kinds of information in a single graph, while still maintaining a clean data model. Those features give graphs a great deal of flexibility for data modeling, as illustrated in Figure 2-5. The figure shows a few things that would be difficult to express in a traditional relational schema, such as different kinds of regional structures in different countries (France has départements and régions, whereas the US has counties and states), quirks of history such as a country within a country (ignoring for now the intricacies of sovereign states and nations), and varying granularity of data (Lucy’s current residence is specified as a city, whereas her place of birth is specified only at the level of a state).