Glossary
Systems engineering, in plain words.
What each term means, why it matters, how it goes wrong, and what Cairn does about it. For the words Cairn itself uses, such as lens, node and ChangeSet, see the docs glossary.
Modeling foundations
- Model-based systems engineeringModel-based systems engineering (MBSE) keeps a system's parts, requirements, interfaces, behavior and verification in one connected model.
- SysML v2SysML v2 is the second major version of OMG's Systems Modeling Language, a standard for writing system models as text or diagrams.
- N² chartAn N² chart is a square matrix with a system's parts on the diagonal and their interfaces in the cells between, showing what each part sends and receives.
Requirements & traceability
- Requirements traceabilityRequirements traceability links each requirement to where it came from, what satisfies it and how it is verified, so the effect of a change can be followed.
- Interface control documentAn interface control document (ICD) defines how two systems or parts connect: what passes between them, in what form, and who is responsible for each side.
- Digital threadA digital thread links a product's engineering data across its life, from requirements and design to manufacturing, test and operation.
- Requirements flowdownRequirements flowdown turns a system requirement into derived requirements on the subsystems and parts that must meet it, each linked to its parent.
Behavior & verification
- State machineA state machine models behavior as a set of states and the transitions between them, each fired by an event and optionally limited by a guard.
- Verification methodsVerification methods are the ways to show a requirement is met: inspection, analysis, demonstration and test, chosen for the evidence each one needs.
- Verification cross-reference matrix (VCRM)A verification cross-reference matrix (VCRM) lists each requirement against the methods that will verify it, so every requirement has a plan.
Decisions & governance
- Trade studyA trade study compares design alternatives against weighted criteria to choose one, and records why the others were set aside.
- Pugh matrixA Pugh matrix compares design concepts with a chosen baseline, criterion by criterion, marking each as better, worse or the same.
- Change controlChange control is the process for proposing, assessing, approving and recording changes to engineering items against an agreed baseline.
- ChangeSetA ChangeSet is a group of create, update and delete operations on a model that applies as one, with a record of each item before and after.
- Technology readiness level (TRL)A technology readiness level (TRL) rates a technology's maturity on a scale from 1, basic principles observed, to 9, proven in actual operation.