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. ---- 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. ---- CategoryDomainEngineering | Contributions by ArieVanDeursen