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

Notes

• The 

  Gloss
  t 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 

  Gloss
  t descendant

   of itself, which means the hierarchy must not contain cyclic 

  Gloss
  t relationships

  . This type of hierarchy is therefore known as a 

  Gloss
  PreSpace false t 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 

Hierarchy Illustration - Polyhierarchical Classification

Alternatives

• Polyhierarchy

Related Links

• Gloss
  t Statistical classification

• Gloss
  t Monohierarchical classification

• Gloss
  t Subtype classification

• Gloss
  t Directed acyclic graph