Table 1:

Attributes from the AOP-KB that were assigned to each key event (KE) and key event relationship (KER)

KE Attribute	Description
KE ID	Unique identifier number for each KE
AOP ID	List of IDs for all AOPs that a KE is a member of
KE Designator	Indicates whether the event a regular key event (KE), a molecular initiating event (MIE), or an adverse outcome (AO)
Level of Biological Organization	Indicates the level of biological organization as either: molecular, cellular, tissue, organ, individual, or population
KER Attribute	Description
KER ID	Unique identifier number for each KER
AOP ID	List of IDs for all AOPs that a KER is a member of
Weight of Evidence*	A value of low, moderate or high that describes the level of confidence in the empirical evidence supporting the KER
Quantitative Understanding*	A value of low, moderate or high that describes the level of quantitative understanding of the KER

^*For KERs that did not have a value specified for these attributes in the AOP-KB, a default value of “low” was assigned.