Arc Skills / Requirements

Identify undefined terms in requirements

Arc Skills compares requirement wording with the controlled glossary and interface definitions. It returns a grouped term register with affected IDs, plausible readings, consequences, and the owner of each clarification.

Use this skill

Use Arc Skills to identify terms whose definitions affect the supplied requirements.

Inputs:
- Requirement set with IDs, exact wording, and revision
- Controlled glossary, interface definitions, and mode or fault taxonomies
- Event and measurement definitions used by linked criteria

Return a grouped term register with affected IDs, alternate readings, consequence, and definition owner.
Flag decision-changing ambiguity, not ordinary vocabulary. Distinguish absent from conflicting definitions

Set up the toolkit · Read the skill instructions

What you provide and what you get

Inputs and outputs
What you have	How it is used	What you get
Requirement set	Finds terms at exact IDs and phrases	Occurrence register
Controlled glossary	Shows existing definitions and gaps	Absent/conflicting verdict
Interface and mode context	Explains why a term matters	Clarification question

Safe mode and fault timing

Illustrative engineering example.

The controlled glossary defines temperature unit °C but has no entries for safe mode or critical fault. It also omits the start and end events for the one-second transition.

R-7: The controller shall enter safe mode within 1 s of a critical fault.
R-8: In safe mode, the controller shall disable output O-1.
Glossary: °C is defined; safe mode and critical fault absent.

Safe mode and fault timing — illustrative output
Term / affected IDs	Plausible readings	Consequence and owner
safe mode / R-7, R-8	Commanded state versus all outputs physically safe	Different end event and O-1 behavior; mode owner defines entry criterion.
critical fault / R-7	All detected faults versus approved fault class	Different trigger set; safety/fault taxonomy owner decides.
within 1 s / R-7	From detection, classification, or annunciation to command or stable state	Timing test can pass or fail differently; verification owner fixes event points.

The unit “1 s” itself is not undefined. The problem is which two events bound the measurement. Resolving that pair can change both the Controller design and its test.

Grouping safe mode across R-7 and R-8 lets an owner make one controlled definition decision. The defined °C term is left out of findings because it has no ambiguity in this scope.

Find terms that move decisions

Scan actors, modes, classes, data names, and timing boundaries.
Check exact controlled definitions and applicability to this revision.
Group repeated occurrences and state two plausible engineering readings.
Route a narrow definition question to the accountable owner.

Questions about this task

Is every missing dictionary definition a defect?

No. Flag terms only when plausible readings alter implementation or pass/fail judgment.

Can a source comment define safe mode?

It can inform a proposal, but it is not a controlled definition unless the project adopts it.

Sources and further reading

NASA Systems Engineering Handbook: Lifecycle and requirements guidance; the example decisions are illustrative.