Deﬁning a Graph Database
A graph database is any storage system that
provides index-free adjacency.45
There is no “oﬃcial” deﬁnition of what makes a database a graph database. The one provided is my
deﬁnition. However, hopefully the following argument will convince you that this is a necessary deﬁnition.
There is adjacency between the elements of an index, but if the index is not the primary data structure
of concern (to the developer), then there is indirect/implicit adjacency, not direct/explicit adjacency. A
graph database exposes the graph as an explicit data structure (not an implicit data structure).