. 2018 Mar 6;9:39. doi: 10.3389/fgene.2018.00039

Table 1.

Interpretation of the 16 R-regulations between vertices u and v for an R-graph.

Meaning	Acronym	Formula
Mandatory, positive, unambiguous	MPU	R⁺∧¬R⁻
Mandatory, negative, unambiguous	MNU	¬R⁺∧R⁻
Mandatory, ambiguous	MA	R⁺∧R⁻
No regulation	NR	¬R⁺∧¬R⁻
Mandatory, positive, possibly ambiguous	MPPA	R⁺
Mandatory, negative, possibly ambiguous	MNPA	R⁻
Mandatory, unknown sign, unambiguous	MUSU	¬(R⁺ ↔ R⁻)
Mandatory, unknown sign, possibly ambiguous	MUSPA	R⁺∨R⁻
Optional, positive, unambiguous	OPU	¬R⁻
Optional, negative, unambiguous	ONU	¬R⁺
Optional, ambiguous	OA	(R⁺↔R⁻)
Optional, positive, possibly ambiguous	OPPA	R⁺∨¬R⁻
Optional, negative, possibly ambiguous	ONPA	¬R⁺∨R⁻
Optional, unknown sign, unambiguous	OUSU	¬(R⁺∧R⁻)
Contradiction	False	0
Tautology	True	1

Each R-regulation is denoted by an acronym. Leaving out trivial regulations false, NR, and true, R-regulations can be classified as optional or mandatory. In the case of no regulation (NR), edges are not depicted. The last column shows the constraint added by Griffin in each case (R⁺ denotes a positive regulation from u to v for the Boolean network f (R⁺(u, f, v)), R⁻ a negative regulation (R⁻(u, f, v)), see definition 3).