Database Reference
In-Depth Information
Admin Areas
Settlements
Landforms
Structures
Building
Places
Place
Road & Rail
FIGURE 10.2
The revised top level of the ontology.
Once we have done this, we can therefore better describe Place as follows:
Every Place is a kind of Feature.
Every Place has part a Feature that
is intended for a Purpose.
Every Place is intended for a Purpose.
Class:Place
SubClassOf: Feature, (hasPart
some Feature that
isIntendedFor some Purpose),
isIntendedFor some Purpose
On the face of it, this seems perfectly logical, but all is not what it may seem. The
problem is that there is nothing that states that the purpose of the Feature that is a
part of the Place has to be the same as the purpose of the Place itself. This problem
can be resolved, as we discussed in Section 10.2.14.4, but even this is not an ideal
solution. For now, Merea Maps decides to settle with this solution because although
it is imperfect, it decides that it is still a useful pattern and does enable general
queries to be constructed.
A further issue is that a Place can of course be just a single Feature; a school
might comprise a single building and nothing else. The description of a school used
previously and the general pattern will deal with this, but in these cases it does
introduce a level of complexity that is strictly unnecessary for such Features; that is
the School is a Place that contains a single building, as opposed to just a building.
One way around this is to redefine Place by making it either a Site or a Building,
where a Site has the old definition of Place (Figure 10.2).
Every Site is a kind of Feature.
Every Site has part a Feature that
is intended for a Purpose.
Every Site is intended for a Purpose.
Every Place is a kind of Site or
Building.
Every Place is intended for a Purpose.
Class: Site
SubClassOf: Feature, hasPart
some Feature that is
IntendedFor some Purpose
Class:Place
SubClassOf: Site or Building,
isIntendedFor some Purpose
Here, Site now represents any collection of Features that are related by some
Purpose, and a Site may have no buildings but does not exclude the possibility of
