07 Reference: acronyms, integrity levels and shorthand labels
Status: DRAFT v1.1, 2026-08-19. Everything in this pack and on the site that is a code, a level, a colour or an abbreviation is defined here. Where a term has a regulatory definition, this page summarises; the regulatory text governs.
1. Integrity levels (L1 to L6)
From ADR-0007 Evidence integrity. Every claim, indicator and barrier carries the level of the evidence behind it. The rule is "classify, record, never round up; state the target separately from the position". A lower number is weaker.
| Level | Name | Meaning | Typical example |
|---|---|---|---|
| L1 | Assertion | Somebody or something said so; nothing independently checks it | Aircraft self-reports its battery state; a firmware version string; a switch position |
| L2 | Custody | Recorded in a tamper-evident chain; alteration or reordering is detectable afterwards, but the origin is not proven | An authority ledger event; a hash-chained record |
| L3 | Attribution | Signed at origin by a known key; who produced it is provable | A signed permit; an agency-signed directive; a signed refusal |
| L4 | Measurement | Measured by the thing itself rather than reported about it | A configuration hash computed on the flight controller over live parameter memory; a refusal to arm (a physical fact) |
| L5 | Independent custody | Periodically anchored with a party the operator does not control, so the record is verifiable against them | Chain-head deposits with the service, a regulator or an insurer |
| L6 | Hardware root of trust | Anchored in silicon that cannot be impersonated from software | A secure element on the module; a secure-boot chain on the computer that produced the evidence |
Integrity is about provenance, not data quality or timeliness; those are separate.
2. Shorthand labels used in this pack and on the site
| Label | Where | Meaning |
|---|---|---|
| SIMULATED | banners, record field simulated: true |
The data comes from the SigNet simulator (the seed corpus or the live demo tenant), never from a real aircraft. Never aggregated with live members' data |
| LIVE, SIMULATED | the live page | Arriving in real time, still from the simulator |
| rule-derived / human | occurrence records (classification) |
How the hazardous-event class and barrier story were assigned: by a documented mapping rule from machine events, or by a person |
| computed / submitted | member indicators (basis) |
An indicator derived by the service from the member's own day-one and occurrence records, or taken from the member's own periodic summary |
| green / amber / red | dossier checklist | Present and in date / present with a gap or expiring within 60 days or link-only / missing or expired. Presence and expiry only; never an assessment of content |
| met / partial / not yet / not applicable | OSO matrix | The member's own declaration per objective; not applicable = the SORA annex table sets no robustness requirement at that SAIL |
| none / low / medium / high | OSO matrix, "required" | Required robustness at the member's SAIL per the SORA annex table |
| LIVE / BENCH / PARTIAL / PLANNED / GAP | hazard library status | Built and exercised in the v1 run / built and proven on the bench only / partly built / designed, not built / missing |
| P / R | hazard library barrier type | Preventive (stops the event) / recovery (limits the outcome) |
| S x L | hazard library risk | Pre-mitigation severity (1 negligible to 5 catastrophic) times likelihood (1 rare to 5 frequent), seed values only |
| O1 to O7 | safety policy objectives | The service's own safety objectives, each measured by an SPI |
| SPI-01 to SPI-17 | indicators | The standard safety performance indicators (03); SPI-17 is the consent-gate indicator, not yet measurable |
| D1 to D5 | indicators | Denominators: flights, flight hours, permits, requests, fleet |
| Tier 0 / 1 / 2 | reporting schema | Record tiers: flight_day_one (exposure) / occurrence / periodic_summary |
| owner / safety_manager / submitter / viewer | member users | Roles: everything incl. invites / submit + onboarding + OSO matrix + keys / submit records and documents / read only |
| invited / onboarding / active / suspended | member status | Lifecycle of a member organisation |
| seed-v1-sim / signet-sim | member ids | The seed corpus tenant / the live simulator tenant (both simulated) |
| HE01 to HE04, NONE | occurrence records, hazard library | The CAA's four UAS hazardous events (below); NONE for near-miss classes that did not reach one (e.g. refusal to arm) |
| nominal / degraded_hold / rtl / divert / emergency_land / terminate | escalation path | The outcome ladder, worst last (ADR-0015) |
| completed / diverted / emergency_landed / refuge_landed / hold_timeout_landed / forced_descent / refused_to_arm / did_not_depart | outcome | What happened to the flight, mapped from ledger events |
| prefix64m | corpus manifest | A fast hash of the first 64 MiB plus size of the 8 GB snapshot; the full hash is recorded on the compressed archive |
| sim_clock_40x | hours basis | Flight hours in the seed corpus are wall-clock duration times the simulator's 40x time scale |
| M0 / M1 / M2 / M3 | module trust | Absent / observe / advise / enforce (ground only) modes of the hardware trust layer |
| S1 to S8 | service catalogue (06) | Schema stewardship, hazard library, SPI service, occurrence workflow, broker, custody, conformance, GA services |
| M1 / M2 / M3 | build milestones | Public site and seed corpus / onboarding and member portal / live tenant |
3. Hazardous events (CAA regulatory SMS for UAS)
| Code | Event |
|---|---|
| HE01 | Loss of control of the UA |
| HE02 | Trajectory conflict with obstacles, terrain or persons |
| HE03 | Trajectory conflict with other airspace users |
| HE04 | Unauthorised airspace access |
Barrier effectiveness (which controls activated, held, did not) is the CAA's stated unit of analysis; the bowtie model sits behind the four events.
4. Acronyms
| Term | Meaning |
|---|---|
| A2 CofC | A2 Certificate of Competency (UK remote pilot qualification, open category A2) |
| AAIB | Air Accidents Investigation Branch (UK) |
| ADR | Architecture decision record (numbered design decisions in the SigNet programme, e.g. ADR-0007) |
| ANSP | Air navigation service provider (NATS in the UK) |
| API | Application programming interface; here, the service's machine interface for records |
| ARC | Air risk class (SORA), initial and residual |
| ARPAS-UK | Association of Remotely Piloted Aircraft Systems UK, the trade association |
| ASTM F3269 | Standard practice for run-time assurance of aircraft systems (the "certify the cage" pattern) |
| ASTM F3548 | Standard for UAS traffic management (UTM) interoperability |
| BSI PAS | British Standards Institution Publicly Available Specification, a fast-track standards route |
| BVLOS | Beyond visual line of sight |
| C3 | Command, control and communications link |
| CAA | UK Civil Aviation Authority |
| CAMO | Continuing airworthiness management (here, the part-life ledger) |
| CAP 722 | CAA guidance for UAS operations in UK airspace |
| CAP 795 | CAA guidance on safety management systems |
| CIC | Community interest company (a UK company form for social purpose) |
| CIS | Common information service (U-space) |
| CLG | Company limited by guarantee (a UK not-for-profit company form) |
| ConOps | Concept of operations |
| CSV | Comma-separated values (the upload format for day-one records) |
| EC 785/2004 | Regulation on minimum insurance requirements for air carriers and aircraft operators (as retained in UK law) |
| ECCAIRS | European Co-ordination Centre for Accident and Incident Reporting Systems, the occurrence-reporting portal |
| ERP | Emergency response plan |
| FC | Flight controller |
| FMEA | Failure mode and effects analysis |
| GA | General aviation |
| GRC | Ground risk class (SORA), intrinsic and final |
| GVC | General VLOS Certificate (UK remote pilot qualification for the specific category) |
| HMI | Human-machine interface |
| ICAO Annex 19 | The international standard for safety management |
| ICO | Information Commissioner's Office (UK data protection regulator) |
| JARUS | Joint Authorities for Rulemaking on Unmanned Systems, authors of SORA |
| JSON Schema | The machine-readable definition of the record formats |
| L1 to L6 | Integrity levels, section 1 |
| M1, M2, M3 (SORA) | Ground-risk mitigations: strategic mitigations / effects of impact reduced / ERP |
| MOR | Mandatory occurrence report (UK Regulation 376/2014 as retained) |
| MoC | Management of change |
| MTOM | Maximum take-off mass |
| NATS | The UK air navigation service provider |
| OA | Operational authorisation |
| OSC | Operating safety case (UK route to an OA) |
| OSO | Operational safety objective (SORA; 24 of them) |
| PDRA-01 | Pre-defined risk assessment 01 (UK standard authorisation) |
| RAE | Recognised assessment entity (assesses remote pilot competency) |
| RPIC | Remote pilot in command |
| RTA | Run-time assurance |
| SAIL | Specific assurance and integrity level (SORA, I to VI) |
| SMS | Safety management system |
| SoC | State of charge (battery) |
| SORA | Specific operations risk assessment (JARUS); versions 2.0, 2.5, and the UK adoption |
| SPI | Safety performance indicator |
| TMPR | Tactical mitigation performance requirement (SORA air risk) |
| UA / UAS | Unmanned aircraft / unmanned aircraft system |
| U-space | The EU framework for UAS traffic management services (not adopted in the UK) |
| USSP | U-space service provider |
| UTM | UAS traffic management |
| VLOS | Visual line of sight |
5. SigNet terms
| Term | Meaning |
|---|---|
| Authority | The SigNet service that issues permits and refusals and writes the ledger |
| Bound request | A single signature over airframe id, configuration hash, attestation hash, route hash, time and nonce; health and route are cryptographically inseparable |
| Permit | Signed authorisation for one flight, bound to configuration, route and energy |
| Gate | A condition that must hold before departure: authority permit, configuration, human consent |
| Refusal | An authority-initiated withdrawal of permission; on the ground it prevents arming, airborne it directs a divert |
| Ledger | The append-only, hash-chained event store (each event's hash covers the previous hash and its payload) |
| Chain head | The hash of the most recent ledger event; depositing it with a third party is independent custody (L5) |
| Segment | A run of ledger events that link perfectly; a break between segments means a write was lost |
| Config hash | The hash over the aircraft's live parameter memory and firmware, measured on the flight controller |
| Refuge | A designated hold point en route where delay is absorbed on the ground, not in the air |
| Contingency ladder | Divert, emergency land, forced descent: the energy-driven recovery sequence |
| Directive | An agency-signed airspace restriction the authority enforces at permit time |
| Seed corpus | The simulated fleet's ledger (2.25 million flights) used to shape the standard; never a safety claim |