Hierarchical data reflects a set of parent-child relationships. These can be found in a genealogy, a taxonomy, a list of requirements for parts assembly, and innumerably other instances. Methods for dealing with hierarchical data are often essential for data management and analysis.
Hierarchical data reflects a set of parent-child relationships. As Materials Resource Planning was developed by manufacturers in the 1950s, hierarchical data management emerged as a theoretical and practical discipline. A manufacturer uses the term Bill of Materials (BOM) for the set of items required to assemble a parent item; the term BOM was adopted by mathematicians and software developers, and it is used today in both realms.
Hierarchical data is ubiquitous and has called forth some of the most important and complex work of database management. It has also propelled object-oriented programming.
The key design element is recursion. Imagine starting at the trunk of a tree and visiting every leaf; this theoretical exercise would require an enormously large number of decision points occurring in a nested or recursive pattern. Requirements for this analysis are remarkably varied and have produced entire sub-disciplines of database design.
