Nodes (ObjectsContainers, Datastreams and NonRdfSourceDescriptions and other resources) in Fedora 4 have a primary type as well as any number of mixin types that define the characteristics of the node. This may include what properties are set, their types, default values, versioning characteristics, allowable children to name just a few. The "Types" link in the navigation bar takes you to a display of all the predefined node types and mixins as well as a form that allows you to update existing or create new mixin types.
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