Appendix E - Hierarchical model. This chapter presents the following content: Basic concepts, tree-structure diagrams, data-retrieval facility, update facility, virtual records, mapping of hierarchies to files, the IMS database system. | Appendix E: Hierarchical Model Database System Concepts, 6th Ed. ©Silberschatz, Korth and Sudarshan See for conditions on re-use Appendix E: Hierarchical Model Basic Concepts Tree-Structure Diagrams Data-Retrieval Facility Update Facility Virtual Records Mapping of Hierarchies to Files The IMS Database System Database System Concepts - 6th Edition ©Silberschatz, Korth and Sudarshan Basic Concepts A hierarchical database consists of a collection of records which are connected to one another through links. A record is a collection of fields, each of which contains only one data value. A link is an association between precisely two records. The hierarchical model differs from the network model in that the records are organized as collections of trees rather than as arbitrary graphs. Database System Concepts - 6th Edition ©Silberschatz, Korth and Sudarshan Tree-Structure Diagrams The schema for a hierarchical database consists of boxes, which correspond to record types lines, which correspond to links Record types are organized in the form of a rooted tree. No cycles in the underlying graph. Relationships formed in the graph must be such that only one-to-many or one-to-one relationships exist between a parent and a child. Database System Concepts - 6th Edition ©Silberschatz, Korth and Sudarshan General Structure A parent may have an arrow pointing to a child, but a child must have an arrow pointing to its parent. Database System Concepts - 6th Edition ©Silberschatz, Korth and .
