traffic light interlock (graphical LD)¶


suite id	`g_traffic_light`
domain	traffic
language	LD-graphical
difficulty	easy
validation status	validated
origin	authored
license	CC-BY-4.0

Authored for this suite to cover this domain with genuine control logic

What is proved¶

From benchmarks/traffic/g_traffic_light/props.yaml. What each kind claims, and what it becomes on either route, is on The properties we prove.

id	kind	claim	requirement
`P1`	`mutual_exclusion`	never true together: `ns_green`, `ew_green`	Conflicting green phases must never be energised simultaneously.

Variants¶

file	expected verdict	violates	method
`clean.xml`	SAFE	none	expert
`bomb.xml`	VIOLATION	`P1`	fault-injection

Files¶

file	what it is	size	sha256
`benchmark.yml`	benchmark metadata	1.0 KB	`e5eefca94287`
`bomb.xml`	ladder program, PLCopen XML	2.9 KB	`6e660342835c`
`clean.xml`	ladder program, PLCopen XML	2.4 KB	`647b0ea73adf`
`props.yaml`	property file	0.2 KB	`108b172e36e2`

Structured text, derived¶

Read off the ladder graph by runner/ld_to_st.py: every rung's contacts and coils rewritten as IEC 61131-3 assignments, in the same series/parallel logic the PLCopen XML encodes. This is a reading aid, not a second source of expected verdicts; ESBMC verifies the ladder program shown above, never this rendering.

bomb.xmlclean.xml

PROGRAM g_traffic_light_bomb
VAR_INPUT
    ns_req : BOOL;
    ew_req : BOOL;
    maint : BOOL;
END_VAR

VAR_OUTPUT
    ns_green : BOOL;
    ew_green : BOOL;
END_VAR


ns_green := ((NOT ew_req OR (ew_req AND maint)) AND ns_req);
ew_green := ew_req;

END_PROGRAM

PROGRAM g_traffic_light_clean
VAR_INPUT
    ns_req : BOOL;
    ew_req : BOOL;
    maint : BOOL;
END_VAR

VAR_OUTPUT
    ns_green : BOOL;
    ew_green : BOOL;
END_VAR


ns_green := (NOT ew_req AND ns_req);
ew_green := ew_req;

END_PROGRAM

Recorded runs¶

A task can carry two routes. ld is ESBMC's ladder front end reading the program directly. via C is the same solver reached through Beremiz and MatIEC, which is the only route that reaches ST, IL, FBD and SFC; see How ESBMC-PLC works.

g_traffic_light__bomb (props.yaml, expected VIOLATION): v8.4 VIOLATION
g_traffic_light__bomb__viac via C (props.yaml, expected VIOLATION): master VIOLATION
g_traffic_light__clean (props.yaml, expected SAFE): v8.4 SAFE
g_traffic_light__clean__viac via C (props.yaml, expected SAFE): master SAFE