Al-Mubaid et al. proposed a semantic similarity measure in their research paper [1]. They see ontologies as connected graphs but refer to clusters within ontology graphs without ever defining what they are.
I am not sure what they meant with clusters.
This is an example of two clusters that Al-Mubaid et al. presented in their paper. The nodes starting with 'a' are part of cluster A, whereas those starting with 'b' are part of cluster B.
There are two possible ways to interpret the definition of clusters:
- The clusters are separate ontologies.
- every root node's branch forms an independent cluster?
[1] Al-Mubaid H, Nguyen HA. A cluster-based approach for semantic similarity in the biomedical domain. Conf Proc IEEE Eng Med Biol Soc. 2006;2006:2713-2717. doi:10.1109/IEMBS.2006.259235