Table 1.

Operational definition of the principles

Principle		Definition
Hierarchical cycles	H1	No is-a hierarchical cycles are allowed.
	H2	No part-of hierarchical cycles are allowed.
Classification	T1	Every non-leaf concept has at least two children.
	T2	Every concept has a reasonable number of children (relative to other concepts in the same ontology).
	T3	In every group of siblings, each concept has specific properties or relations to other concepts.
	T4	Every non-leaf concept is classified according to a single criterion.
Incompatible relationships	R1	For every pair of concepts x and y, x and y do not have both is-a and part-of relationships.
	R2	For every pair of concepts x and y, x and y have at most one kind of the four part-of relationships: constitutional part of, systemic part of, regional part of and 2D part of.
	R3	For every pair of concepts x and y, x and y do not have both branch of (or tributary of) and hierarchical relationships (is-a or part-of).
Dependence	D1	Concept Subdivision of x (or Organ component of x) does not exist unless concept x exists.
	D2	Term containing the word “wall” indicates that the corresponding concept has part-of relationship to some larger concept.
Co-dependence of equivalent relations	C1	The co-dependence between equivalent relations 〈x, is-a, Subdivision of y〉 (or 〈x, is-a, Organ component of y〉) and 〈x, part-of, y〉 must be identified.
	C2	The co-dependence between equivalent sets of relations {〈x, is-a, y〉, 〈y, part-of, z〉} (or 〈x, part-of, y〉, 〈y, is-a, z〉}) and 〈x, part-of, z〉} must be identified.
Implicit relations	I1	The implicit relations are consistent within themselves.
	I2	The implicit relations are consistent with explicit relations.