Arc Skills / Interfaces
Write an interface control document
An ICD controls agreed detail for a defined System pair, including what is still undecided. Arc Skills takes endpoint and source documents and returns a controlled draft rather than treating a nominal match as release approval.
Use this skill
Use Arc Skills to draft an Interface control document for my agreed System pair.
Inputs:
- Interface ID, endpoint owners, configuration, source revisions and document status
- Controlled exchange parameters with direction, units, tolerances and modes
- Discrepancies, verification approach, approval owners and open decisions
Return a revisioned draft with scope, parameter/source table, TBD owners, verification rows and approval placeholders. Do not present a nominal match or unapproved draft as released compatibility.What you provide and what you get
| What you have | How it is used | What you get |
|---|---|---|
| Interface identity and revisions | Fixes exact endpoints and controlled source set | Draft scope and revision block |
| Parameter evidence | Reconciles supplier and receiver values | Source-linked parameter table |
| Owners and verification plan | Makes closure and release responsibilities visible | TBD, verification and approval rows |
Controller–sensor ICD draft excerpt
Illustrative engineering example.
The fictional interface is electrical power from a controller to a sensor. The controller description states 28 V nominal; the sensor accepts 22–30 V input. No controller output tolerance is supplied, so this is a revisioned draft with an explicit unresolved parameter, not a released ICD.
ICD ID: IF-07 | Draft revision: A | Release: not approved
Endpoints: controller power output → sensor power input
Source C-1: controller data, rev A | Source S-1: sensor sheet, rev B
Approvals: controller owner signature TBD; sensor owner signature TBD| Parameter / section | Controller side | Sensor side | Status and action |
|---|---|---|---|
| Nominal supply, electrical | 28 V nominal (C-1 rev A) | 22–30 V accepted (S-1 rev B) | Nominal point inside range; output envelope unproven |
| Output tolerance, electrical | TBD, controller owner | Must remain within 22–30 V | Open; obtain minimum/maximum at sensor pins |
| Power return, electrical | Return pin TBD | Return pin TBD | Open; reconcile connector views |
| Verification V-1 | Characterize output min/max at sensor pins across stated modes | Compare with 22–30 V input envelope | Planned check; acceptance procedure after output tolerance is agreed |
The arithmetic check is narrow: 22 ≤ 28 ≤ 30 V. It shows only that the nominal point sits inside the sensor’s accepted interval. If the controller can produce 31 V in a relevant condition, the interface could still fail. The missing tolerance is therefore a named controller-owner decision, not a blank to be filled with a common percentage.
The excerpt includes identity, revisions, exchange parameters, unresolved decisions and a verification row. Approval placeholders remain unfilled because no sign-off occurred. Once both owners agree the output envelope, connector return and test conditions, they can finalize a verification procedure and review the document for controlled release.
Assemble the controlled draft
- State document ID, revision status, exact endpoint configuration and governing sources.
- Tabulate each exchanged parameter with direction, units, both sides and source revision.
- Keep discrepancies and TBDs tied to decision owners; avoid making a nominal point into a guarantee.
- Write verification rows and approval placeholders before routing the draft for owner review.
Questions about this task
Is this the same as defining an Interface?
No. The Interface proposal names the crossing and owners; the ICD records detailed controlled parameters and verification for that pair.
Can a draft with TBDs be shared for review?
Yes, if clearly marked draft and the open decisions are visible. It should not be represented as an approved compatible interface.
Sources and further reading
- NASA Systems Engineering Handbook: product realization: Interface definition, integration sequence and verification context.
- NASA Systems Engineering Handbook: system design processes: Stakeholder expectations, logical decomposition, functional allocation and design decisions.