Hierarchical and relational databases

There are differences between the hierarchical model for IMS™ databases and the standard relational database model.

IMS presents a relational model of a hierarchical database. In addition to the one-to-one mappings of terms, IMS can also show a hierarchical parentage through the primary or foreign key constraints.

For a comparison of the hierarchical and relational database models, see Comparison of hierarchical and relational databases.