The VR Schema describes multiple composite objects, which are grouped under four abstract classes: Variation, Location (Abstract Class), State (Abstract Class), and Interval (Abstract Class). These classes and their relationships to the representation of Variation are illustrated here. All classes have a string type. Dashed borders denote abstract classes. Abstract classes are not instantiated. Thin solid borders denote classes that may be instantiated but are not identifiable. Bold borders denote identifiable objects (i.e., may be serialized and identified by computed identifier). Solid arrow lines denoted inheritance. Subclasses inherit all attributes from their parent. Inherited attributes are not shown. These abstract classes and their concrete child classes are described in the following documents.