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Glossary

Glossary

abstract definition

An abstract definition has no direct instances: every instance must also be an instance of a concrete definition or usage that specializes it.

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allocation

Assigning functions to logical components, and components to parts: SEBoK’s idea, SysML v2’s allocate, Douglas’s grouping.

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appropriateness

Whether the inference, context or evidence is right for the argument’s application and purpose (Hawkins pairs it with sufficiency for inferences and trustworthiness for context and evidence).

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architecture

The fundamental concepts or properties of a system in its environment, embodied in its elements, their relationships, and the principles of its design and evolution.

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asserted context

Each time context or assumption is introduced, it is asserted to be appropriate for the argument elements it applies to.

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asserted inference

Each time a claim is said to be supported by other claims, an assertion is made that the inference is appropriate and sufficient.

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asserted solution

Each time evidence is cited as a solution, it is asserted to be sufficient to support the claim.

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assumption

Contextual information enters an argument as context or assumption elements, each carrying an assertion of appropriateness.

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assurance claim point (ACP)

The place in the safety argument where an assertion is made; a confidence argument is developed for each.

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assurance deficit

Any knowledge gap that prohibits total confidence.

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behavior

The emergent outcome of a system in use; not prescribed but derived by analysis or simulation and judged against intent.

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concept

The stage before any formal definition of the system: problem statement, needs and requirements.

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confidence argument

The component that justifies the sufficiency of confidence in the safety argument.

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conjugated port

A port usage typed by the conjugate of a port definition: the same features with in and out reversed, written with a ~. It conforms to usages of the original port definition.

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control law

A rule mapping the control error to the actuation command.

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counter-evidence

Recognising assurance deficits guides the search for where counter-evidence may exist.

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decomposition

Decompose a function until implementable system elements can be identified: the stopping criterion for functional decomposition.

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definition

A definition element classifies a kind of element (a classification of attributes, parts, actions and so on).

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design

Activities that create concepts and models to answer an intended purpose; the outcome is a coherent, purposeful set of models or representations.

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dynamical system

A system whose behavior changes over time, often in response to external stimulation.

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emergence

Properties or behaviors that arise at the level of the whole and cannot be attributed to any one component. SEBoK distinguishes simple, weak and strong emergence.

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feature chain

Two or more qualified names separated by dots, each resolved inside the one before it, naming a deeply nested usage, for example the end of a connection.

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function

A transformation of input flows to output flows, with defined performance.

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functional architecture

Intended behavior, stated solution-independently: functions with typed flows, the phenomena relations among them, and the MoEs.

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interface

A shared boundary between two functional units, defined by characteristics of the functions, physical signal exchanges and more.

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judgment

Completely mitigating all assurance deficits is not normally achievable, so a judgment on when they can be tolerated is necessary, assessed by expert judgment of likelihood and severity.

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judgment record

A persisted, checkable record of one judgment call: claim, subject, criteria, premises, evidence, rationale, counter-evidence, residual uncertainty, disposition. It documents reasoning; it proves and approves nothing.

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logical architecture

Prescribed mechanisms and policies carried by logical components, plus the interfaces between them; MoP thresholds are derived here.

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This tutorial uses this term differently from SEBoK.

logical component

The prescribed carrier of a mechanism, with its interfaces; modeled here as an abstract part definition that performs an action.

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measure of effectiveness (MoE)

A measure of stakeholder satisfaction with the outcome: a measurable attribute with a unit and a means of collecting data (for the toaster, how evenly the bread is toasted). Stated at the functional layer.

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measure of performance (MoP)

An engineering measure of performance: a measurable attribute with a unit and a means of collecting data (for the toaster, power efficiency). It characterizes a requirement, which also needs a threshold. Typically logical.

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mechanism

A prescribed, comparatively deterministic input-to-output relation: a modeling decision grounded in engineering practice, a law we use to reason about behavior. Not itself the behavior.

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part definition

A part can be a purely logical component without implementation constraints, a physical component with a part number, or something in between.

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perform action

A perform action usage in a part definition or usage makes the part the performer of the action.

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physical architecture

Concrete parts that realize the logical components and confer values; each must fit the logical interfaces and meet the derived thresholds.

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policy

Decision guidance that selects inputs given the state, typically to close the loop under uncertainty; designed given the available mechanisms.

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query

A query selects Data objects from a project by scope, the properties to return, a constraint (where) and an ordering; it is the standard’s way to interrogate a model.

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requirement

A statement of an operational, functional or design characteristic or constraint that is unambiguous, testable or measurable, and necessary for acceptability.

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safety argument

The component of an assured safety argument that documents the arguments and evidence used to establish direct claims of system safety.

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selection among alternatives

Choosing among alternative mechanisms by trade study against the derived measures.

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simulation

A model that behaves like a given system when given controlled inputs.

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specialization

A definition is specialized by subclassification; the specialized definition inherits the features of the more general one and can add others.

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sufficiency

For inductive arguments, the probable truth of the premises is sufficient to establish the probable truth of the conclusion.

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technical performance measure (TPM)

The value assessed on a design element by analysis or simulation: the evidence against a MoP threshold.

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traceability

The degree to which a relationship can be established between two or more development products.

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trustworthiness

Freedom from flaw, argued by considering the processes that generated the artefact.

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usage

A usage is a usage of a definition in a context; it must be defined by at least one definition of its kind.

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validation

Confirmation, through objective evidence, that stakeholder requirements for an intended use have been fulfilled: the right system was built.

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verification

Confirmation, through objective evidence, that specified requirements have been fulfilled: the system was built right.

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view

A view definition specifies how to create a view artifact (a rendering of information for stakeholders) from conditions that extract the relevant model content plus a rendering.

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Chapter 10: Traceability and Sign-off
Reproducibility
Chapter 10: Traceability and Sign-off
References