The GJXDM consists primarily of object classes and properties. The Object classes are converted into XML Schema types. They eache represent a specific syntax and structure for a set of values. The properties are converted into XML Schema attributes and elements. They each represent characteristics, or values of things.
The GJXDM is a reference model that is based on a class hierarchy of many specific objects (xsd:type) derived from one very general object (SuperType). Each object contains any number of properties (xsd:element or xsd:attribute). These properties may be simple or complex elements (containing sub-elements). The highest level object classes (under the SuperType) are PersonType, OrganizationType, PropertyType (i.e., things), LocationType, ContactInformationType (i.e., electronic means of contact), ActivityType, DocumentType, and other smaller supporting types.
There is also a special class of RelationshipType used to specify meaning to a link between two object instances. On many of these objects, there are metadata properties (xsd:element or xsd:attribute) that supplement meaning. For example, all properties of MeasureType have a mandatory "units" attribute.