TopicDB is a topic maps-based graph library. TopicDB is an open source project maintained at GitHub.
The topic maps paradigm describes a way in which complex relationships between abstract concepts and real-world resources can be described. The fundamental components of topic maps are topics, associations and occurrences.
The most significant attributes of a topic are its unique identifier and names. Essentially, a topic acts as a stub to which you can attach resources and refer to in associations.
Occurrences are those resources that you have attached to a topic; for example, text, images, PDF files, or links to other web pages.
The notion of a topic is at the heart of the topics map concept. However, without associations to actually connect the topics to each another in a semantically meaningful way, a topic map would be of little practical use.