Database Reference
In-Depth Information
administrative regions, land forms, and structures, whereas the Land Cover Ontology
will differentiate depending on physical form and will discriminate between vegeta-
tion, solid surfaces (such as roads and rock), and water.
Using this Land Cover Ontology, Merea Maps can now reasonably say the following:
Every Woodland has part Trees.
Class: Woodland
SubClassOf: hasPart some Tree
This raises the question of how we view a tree: Is it a Feature in the same way that
a building is? Strictly, yes, because it can certainly be located on the land's surface,
but there are some differences in the way we should view Buildings and Trees. With
buildings, we are normally interested in individual buildings; this is rarely true with
trees. Although Merea Maps does occasionally map specific notable trees, this is
very far from the norm, and it would be a ludicrously obsessive mapping agency
that mapped every individual tree in a woodland. Coming at this from the direction
of land cover then, this issue would never even be considered—the cover is always
about collections, not individuals. So, perhaps “has part” is an inappropriate property
in this case. Merea Maps therefore introduces a new relationship for its land cover
types: “has cover of.” In fact, it also creates two subproperties, “has dense cover of”
and has “sparse cover of,” as these are also required to differentiate between differ-
ent types of land cover density. What Merea Maps does not attempt to do is state a
precise differentiation between dense and sparse. Although this might seem to be
introducing imprecision, it reflects the fact that it is almost impossible to be precise
simply because only rarely do people go to the trouble of accurately measuring the
density of tree cover. Normally, estimation is based on the eye, and crude differen-
tiation between dense and sparse is sufficient. So, what may be seen as imprecision
in the ontology is actually just reflecting normal working practices and a pragmatic
acceptance of something that is fit for its purpose. Now, Merea Maps states:
Every Woodland is a kind of
Landform.
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Every Woodland has dense cover of
Trees.
Class: Woodland
SubClassOf: Landform
Facts: hasDenseCoverOf some
Tree.
These new properties can be used to help describe individual instances of Feature
types. For example, Isis Heath can be described in the following terms:
Every Heath is a kind of Unenclosed
Land.
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Every Heath has dense cover of
Heather.
Isis Heath is a Heath.
Isis Heath has sparse cover of Trees.
Isis Heath has sparse cover of
Boulders.
Class: Heath
SubClassOf: UnenclosedLand that
hasDenseCoverOf some Heather
Individual: IsisHeath
Facts: hasSparseCoverOf some
Tree, hasSparseCoverOf some
Boulder
This tells us that Isis Heath not only has a dense covering of heather (a necessary
condition of a heath) but also has a scattering of trees and boulders.
