Part of

From HAO Wiki

This relationship is relatively intuitive. From the relationship ontology:

id: OBO_REL:part_of
name: part_of
def: "For continuants: C part_of C' if and only if: given any c that instantiates 
C at a time t, there is some c' such that c' instantiates C' at time t, and 
c *part_of* c' at t. For processes: P part_of P' if and only if: given any p that 
instantiates P at a time t, there is some p' such that p' instantiates P' at time t, 
and p *part_of* p' at t. (Here *part_of* is the instance-level part-relation.)"
[PMID:15892874]
comment: Parthood as a relation between instances: The primitive instance-level 
relation p part_of p1 is illustrated in assertions such as: this instance of rhodopsin 
mediated phototransduction part_of this instance of visual perception. This relation 
satisfies at least the following standard axioms of mereology: reflexivity (for all p, 
p part_of p); anti-symmetry (for all p, p1, if p part_of p1 and p1 part_of p then p and p1 
are identical); and transitivity (for all p, p1, p2, if p part_of p1 and p1 part_of p2, 
then p part_of p2). Analogous axioms hold also for parthood as a relation between spatial 
regions.    For parthood as a relation between continuants, these axioms need to be 
modified to take account of the incorporation of a temporal argument. Thus for example the 
axiom of transitivity for continuants will assert that if c part_of c1 at t and c1 part_of 
c2 at t, then also c part_of c2 at t. Parthood as a relation between classes: To define 
part_of as a relation between classes we again need to distinguish the two cases of continuants
and processes, even though the explicit reference to instants of time now falls away. For
continuants, we have C part_of C1 if and only if any instance of C at any time is an
instance-level part of some instance of C1 at that time, as for example in: cell nucleus
part_ of cell.
inverse_of_on_instance_level: OBO_REL:has_part
is_reflexive: true
is_anti_symmetric: true
is_transitive: true

Using coxa part_of leg as an example, it's important to understand a few things about the part_of relationship:

• any instance of coxa (e.g., the coxa of that ant under the microscope) must be part of a leg (i.e., the existence of a coxa means that a leg must also exist)
• a leg does not necessary have a coxa as one of its parts