Relationships between spatial objects
These specifications recognise that there are many different types of spatial data in agriculture. Some entities are related spatially, while others are related in other ways. Our specifications define a number of different entities that may be spatially linked, but not "contained".
For instance, a local council rating unit (often called a "property") may "contain" or "be built up from" individual land titles. However, an operating farm unit (a "holding") may spatially overlay a "property", but may also lease land from adjoining properties, or exclude land leased to a neighbour. It may also overlay reserve land or paper roads that are not part of the "property".
A holding may comprise several land management units ("sites") but they might not cover the full extent of the "holding". For instance, a lake or stream might be excluded.
Cultivated land, permanent crops, and managed livestock areas ("plots", which represent paddocks, crops, and horticultural crops) likely fit within the land management "sites" and therefore a holding. However, plots may not cover the full spatial extent of sites and holding. There may be land that is not actively farmed, including buildings, forests, and other land uses.
The figure below shows how spatial features may occupy similar spatial area while not being completely related.
Thanks to Sam Ragnarsson for the base diagram.
Each spatial entity derived from the base ResourceType class has a set of Links, which can be used to link to other related objects.
Spatial entities may also have relationships with non-spatial entities. For instance, an operating farm (holding) may be associated with the business that runs that farm (an Organization) or even the principle contact person (a Person) or official contact point (ContactPoint).
Our specification does not define these entities, but instead relies on the entity definitions provided by schema.org. Schema.org defines data models for many common entities, such as Organization, Person, and ContactPoint.
At the time of writing, schema.org does not provide a JSON-Schema version of its entities, but charlestati has created a generator and a set of schemas that you can use. There is a Datalinker-Org fork of this repository that you can use.