A transitive parthood relation in which one entity is part of another entity, and the relation is valid for use between continuants or between occurrents but not between a continuant and an occurrent. The part_of relation between continuants is time-dependent while between occurrents it is time-independent.

Interpretation of part_of relation between any two continuant classes

If C and C1 are continuant classes, then C part_of C1 means that every instance of C, at any time, is part of some (one or more) instances of C1 at the same time.


  • Carboxyl Group part_of Carboxylic Acid
  • Dendrimer Generation Layer part_of Dendrimer

Interpretation of part_of relation between any two occurrent classes

If P and P1 are occurrent classes, then P part_of P1 means that every instance of P is part of some instances of P1.


Sample Preparation part_of Study


  • Smith B, Ceusters W, Klagges B, Kohler J, Kumar A, Lomax J, Mungall C, Neuhaus F, Rector AL, Rosse C: Relations in biomedical ontologies. Genome Biol 2005, 6: R46.
  • Schulz S, Kumar A, Bittner T: Biomedical ontologies: What part-of is and isn’t. J Biomed Inform 2006, 39:350-361.