In the network model, data is represented as collections of records, and relationships
are represented by sets. Compared with the relational model, relationships are explicitly
modeled by the sets, which become pointers in the implementation. The records are
organized as generalized graph structures with records appearing as nodes (also called
segments) and sets as edges in the graph. Figure 2.5 illustrates an instance of a network
schema for the same data set presented in Figure 2.4. The most popular network DBMS is
Computer Associates’ IDMS/ R. We discuss the network data model in more detail on the
Web site for this book (see Preface for the URL).