Chapter 8 - Other Models for Trees

Abstract

The chapter discusses the models that use different approaches and properties of trees, some of which are hybrids of other models. These models include models such as adjacency list with self-references and subordinate adjacency list. Subordinate adjacency list is a modification of the usual adjacency list model and shows the edges of a graph as oriented from the superior to the subordinate. Nodes without a subordinate are leaf nodes, and they have a null value. Adjacency list with self-references are also slight modification of the usual adjacency list model and include an edge that loops back to the same node. The chapter also discusses hybrid moles, such as adjacency and nested sets model, nested set with depth model, adjacency and depth model, and computed hybrid models. The chapter also discusses the problem of inability of the nested set model to represent more a general graph in SQL.