The metadata that make up the Horizon Schema are described in the next three subsections. In Appendix A.2.1, dataset-level metadata are presented; these are names that might be returned by a Viewable's getMetadata() method. Appendix A.2.2 lists metadata related to a dataset's world coordinate system. These metadata would normally be sub-metadata of the CoordinateSystem metadatum, making up part of the dataset level metadata; they would also be returned as top-level metadata (i.e. not sub-metadata) by a CoordinateSystem's getMetadata() method. Finally, Appendix A.2.3 gives the metadata related to a single coordinate axis. These metadata would normally appear as sub-metadata of each element of the Axes metadatum.
The Horizon schema uses the convention that names begin with a lower-case letter unless they are of either type Metadata or type Metavector. The capitalization of the first letter therefore indicates that the metadatum contains sub-metadata. For example, the CoordinateSystem metadatum is of type Metadata which can contain the sub-metadatum CoordinateSystem.name. The Axes metadatum is of type Metavector; it may therefore contain the sub-metedatum Axes[1].type.