# Metric

#### Definition:

A System of related measures that facilitates the quantification of an Attribute.

Alternative Names

Concept Number: *095
English Master: Metric
Synonyms, Variations & Acronyms: none

#### Detailing

The Metric may be composed of one or more Measure dimensions or characteristics.
For example “Mean time between failure in operation” – has 3 defining Concepts – “time”, “failure” and “in operation”. This includes one “measure” (time).

A Complex Attribute specification, meaning one defined with a set of several Scales of Measure, is also a Metric expression. There is no implication that a Metric is “Elementary” (that it has only a single Scale).

A “Scale (of Measure)” Parameter, or a set of them, is the way we specify metrics in Planguage.

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#### Type

Type [Metric *095]: Numeric Value.

#### Examples

Examples (Metric Expressions):
Scale: Mean Time Between Failures.

Use: Scale: Time to Learn defined [Average Task]. Past: 30 minutes.

Design A: Impacts Requirement B: 30%.
Each of these 3 statements is based on a “metrics culture.”

Examples (Non-Metric Expressions):
Reliability

“Easy to learn”.

“Very effective design”.
Each of these 3 expressions is based on a “non-metrics culture.” Nice words – no numbers expressed, defined or implied.

#### Notes

1. Metrics are used to express “Concepts of variability” clearly – in particular more clearly than mere words [GILB76].
2. The rationale for using metrics includes:
• to increase Clarity and unambiguousness of specifications
• to increase sensitivity to small changes in specifications and the System itself
• to enable Systems-Engineering logical thinking about relationships – for example the relation of designs to Requirements
• to provide a better Basis for legal contracting about Systems
• to enable Evolutionary tracking of progress towards Goals
• to enable a Process of learning within projects and Engineering and management domains
• to force engineers to think more clearly and communicate more clearly with others

3. A Metric can be used to express the numeric Impact of a design on a Performance-Requirement (for example, when using the Value-Decision method).

#### Keyed-Icons

-|-|-> “Scale with units” or ---> “Scalar Arrow, a simplified Keyed-Icon without explicit units”.
Several other defined Keyed-Icons can also be used to express a Metric (For example, Tolerable and Goal: O---!>-->).

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Scale *132
Meter *094
Measure *132
Level *337

#### History-of-Concept

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This Concept entered by Adore Shuko.