Verifying the Safety of Aviation Software Based on Extended Colored Petri Net

Table 2

The safety requirement level of component (place).

Place	Component	Safety requirement Level	Color of Token
P2	Navigation Subsystem	B	orange
P4	Controller	C	blue
P5	External Subsystem Event Handler	Null	black
P6	Navigation Database Monitor	Null	black
P7	Navigation Monitor	Null,	black
P8	Heading and Speed Monitor	Null	black
P10	Navigation Database Subsystem	C	blue
P12	Heading And Speed Subsystem	A	red