polyhierarchy

polyhierarchy

This is an abbreviation for polyhierarchical classification.

polyhierarchical classification

A hierarchy in which each node has one or more parents.

Notes

• The subtype relationships of SNOMED CT create a polyhierarchical classification.

• A polyhierarchical classification can be represented as a graph in which each node has a one or more directed links to or from other nodes.

• A node in a polyhierarchical classification cannot be a descendant of itself, which means the hierarchy must not contain cyclic relationships. This type of hierarchy is therefore known as a directed acyclic graph.

Examples

• The diagram below shows a polyhierarchy. Each node has one or more parent node so there can be multiple paths from a node to the top (or root) of the hierarchy. For example from node V the paths include the following:

  • V→N→F→B→A

  • V→N→F→C→A

  • V→G→C→A

Figure 1: Hierarchy Illustration - Polyhierarchical Classification

Alternatives

• Polyhierarchy

Related Links

• Statistical classification

• Monohierarchical classification

• Subtype classification

• Directed acyclic graph

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