Network model databases have been viewed as strictly non-relational and outdated. But in the 1990s when the SQL standard incorporated support for declared foreign keys to represent inter-table relationships, the gap between the relational and the network model representation of a database narrowed. This was exploited by Raima in RDM Server (RDMs) with the introduction of the create join statement that allowed an SQL foreign and primary key relationship to be explicitly mapped into a network model set.
In 2009, when Raima decided to add SQL to RDM Embedded®, RDMe, we decided to keep RDMe SQL as simple and as free of as many unnecessary, non-standard extensions as possible. Hence, network model sets are automatically (i.e., implicitly) used in the implementation of foreign and primary key relationships. I’ve recently written a short white paper on this subject that provides a brief historical background of the network database model along with a description of how network model sets are implemented in the RDMe core-level database engine, the syntax and semantics of SQL foreign and primary keys, and why the use of network model sets provides an efficient and high performance implementation for them. I think that you will find it both informative and helpful in increasing your understanding and appreciation for this unique technology.
View the RDMe SQL whitepaper.