Glossary

Ambiguity group: Failure modes that the available tests cannot tell apart.
Balance: The diagnoser setting that trades test cost against information gain.
Capella: A model-based systems engineering tool. MBDlyb can import its models.
Cluster: A container that structures the model hierarchically, for example a subsystem. See Clusters and names.
Composite function: A function with subfunctions.
CPT
Conditional probability table: The table that gives the probability of each state of a node for every combination of parent states. See Conditional probability tables.
Diagnostic procedure
DP: A decision tree of tests that diagnoses the failure modes with one signature.
Diagnostic test: An action with a cost that gives one or more test results.
Direct observable: Information that is available without doing a test, for example a status LED.
Evidence: Information entered in the diagnoser: operating modes, observations and test results.
Fault
Failure mode: A state of hardware other than Healthy, for example Broken. In design for diagnostics, a failure mode is a hardware/fault combination.
FNR
False negative rate: An observable or test result parameter for the chance that an actual failure is missed.
FPR
False positive rate: An observable or test result parameter for the chance that a failure is reported while everything works.
Fully qualified name
FQN: The unique name of an element: the cluster path followed by its name, for example CDRadioPlayer.CDReader.Laser.IlluminateCD.
Function: Something the system does. It works (Ok) or not (NOk), or has custom states.
Hardware: A physical part that can fail. It has the state Healthy and one or more fault states.
Information gain: The expected reduction of uncertainty (entropy) about the diagnosis when you perform a test.
Leaf function: A function without subfunctions. Required for relations must connect leaf functions.
Neo4j: The graph database that stores MBDlyb models.
Observed error: An error code that one function generates and another function reports to the user.
Operating mode: A situation of the system, for example BatteryPower, that determines which required for relations are active.
Operating mode selector: A model element whose states are the operating modes.
Prior: The probability of a fault before there is any evidence. This is a fault rate.
PVMT: The Capella Property Values Management Tools add-on, used to annotate Capella models with diagnostic information.
Root cluster: A cluster without a parent. It represents a complete model.
Signature: The pattern of observable values that a failure mode causes.
Soft evidence: Uncertain evidence, entered as probabilities instead of one state.
Test result: The outcome (Ok/NOk) of a test. It indicates a set of functions and hardware.
Weight: A number between 0 and 1 for how strongly a failure propagates along a relation. See Relation weights.