A.20:0 - Use this when

Use A.20 when one transformation or one operation application is current in a transformation-flow structure and the question is whether that subject satisfies one named internal constraint for one stated case. It also applies when an A.6.4 bounded-use assertion q is current there and q’s exact proposition is the named internal constraint. A.6.4 retains the separate current-case judgement.

First useful move. Write one sentence:

For subject S and case facts I, constraint C is applicable and required; test T returned outcome O under window W, with witness or reason R.

Quick worked case. TemperatureConversion-7 must add 273.15 to a Celsius input and must not return a value below 0 K. For input 25 °C, the test returns 298.15 K, so both required conditions are satisfied; the witness records the formula edition, input, output, and test result for this evaluation window. The practitioner may reuse this result for that case and window, or pass it to a current gate or assurance use; changed input, formula edition, assumptions, or window requires another check. If the output were 297.15 K, the formula condition would be violated; if no output could be recovered, it would be unknown; if the test had not run, its evaluation state would be notRun.

Stop after that result unless a gate, assurance argument, publication, or another named task needs it. Path and crossing structure, refresh, gate decisions, evidence, assurance, Work, and semantic bridges keep their own patterns. What goes wrong if missed. A class label or green status replaces the actual constraint and test. An unknown or unrun required check disappears inside pass. A failed local constraint makes unrelated gate-fit facts look inapplicable. A.20 then starts redefining paths, publications, refresh, gates, or retargeting instead of reporting its own result.

What this buys. A practitioner can see which constraint was tested, why it applied, what case was used, what the result means, and which later decision may consume it.

Not this pattern when.

• Use A.21 for a gate decision or profile consequence.
• Use E.18 for transformation-flow positions, paths, crossings, valuations, or PathSlice identity.
• Use E.17 for publication forms and faces, G.11 for refresh work, and C.27 for temporal-claim adequacy.
• Use A.6.4 for retargeting semantics and F.9 only for a separately claimed semantic correspondence.
• A Signature, WorkPlan, dated Work, or gate check does not enter A.20 merely because it occupies an E.18 position; use the pattern that defines the actual claim.