«MemberOf» is a parthood relation between a functional complex or a «Collective» (as a part) and a «Collective» (as a whole).

Examples include:

  1. a tree is part of forest;
  2. a card is part of a deck of cards;
  3. a fork is part of cutlery set;
  4. a club member is part of a club.

«MemberOf» relation obeys weak supplementation principle (at least 2 parts are required, may be of different types). The memberOf relation is intransitive.

For example, Kazi, Bobek, Nemo and others are members of the TJ Sokol Zizkov Youth Tourist Club. The TJ Sokol Zizkov Youth Tourist Club is the member of the Association of the Youth Tourist Clubs. But Kazi, Bobek, Nemo and others are not members of the Association of the Youth Tourist Clubs, since not persons but only clubs may be members of the association. Although transitivity does not hold across two «MemberOf» relations, a «MemberOf» relation followed by «SubCollectionOf» is transitive.


C1: This relation can only represent essential parthood if the object representing the whole is extensional (i.e. provided that adding or removing of any member changes the identity of the collective). In this case, all parthood relations in which the whole is extensional are constrained as {essential} parthood relations.

C2: The classifier connected to the whole end must be a «Collective». The classifier connected to the part end can be either a «Collective» or functional complex.

Common questions

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EX1: MemberOf Relation

See also Part-Whole.


GUIZZARDI, Giancarlo. Ontological Foundations for Structural Conceptual Models. Enschede: CTIT, Telematica Instituut, 2005. GUIZZARDI, Giancarlo. Introduction to Ontological Engineering. [presentation] Prague: Prague University of Economics, 2011.