Part of the FeatureModel giving a graphical representation of variable and common concept features.
Feature diagrams distinguish between mandatory, optional, alternative, and or-features. Feature diagrams were originally proposed in the FeatureOrientedDomainAnalysis method.

An _instance_ of a feature diagram is a valid set of features.
One diagram generates a series of instances.

See section 4.4.1 of GenerativeProgrammingBook.

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See also:
	* http://www.boost.org/more/feature_model_diagrams.htm for a textual version of feature diagrams.
	* DomainSpecificLanguageDesignRequiresFeatureDescriptions, which includes feature manipulations as well as several examples.

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CategoryDomainEngineering | Contributions by ArieVanDeursen