This text discusses how to implement access control lists using a graph database, specifically with Ruby bindings for the Neo4j graph database. The application provides user permissions to access, create, or change resources, such as a file system. The system uses a graph structure with nodes representing principals (users and groups) and content (folders and files), and relationships between them. The authors explain how to create the basic structure of the graph, including subreference nodes for principals and content, and security relationships with optional boolean flags for read and write permission. They also provide algorithms to retrieve permission flags and print permission information. The example application demonstrates how to use these concepts to implement access control lists in a file system.