Database Reference
In-Depth Information
46
Minerva Row
13
57
FIGURE 6.3
Isis houses.
they do not provide all the answers. Geography frequently lacks the certainty of
hard geometry because precise geometric definitions may be unknown or simply not
defined or because people operate at varying levels of detail. People also tend to use
a whole host of inexact terms when referring to the spatial properties between two
features. Let us look at an example, again using the “next to” property.
We have seen how we can use OGC Geo properties that are based on RCC8 to
represent topological relationships, but now consider not the cottages on Ash Fleet
Farm estate but some of the houses in the village of Isis (Figure 6.3).
The “next to” property as Merea Maps have currently designed it will work if we
are operating at the level of a property (house and gardens) as follows:
4 Minerva Row is next to 6 Minerva Row.
8
8 Minerva Row is next to 10 Minerva Row.
But, we cannot say that
10 Minerva Row is next to 12 Minerva Row.
as there is a path between the two properties, so they are geometrically disjoint.
However, not everyone operates at this detailed level, or they may be generally less
concerned about precise geometry; Merea Heritage would regard a path as irrelevant,
and even Merea Maps when implementing its place name gazetteer will not be inter-
ested in the absolute detail of its topographic maps. Similarly, two detached houses
each surrounded by adjoined gardens might be considered to be next to each other at
one level of resolution: that of the property not the building. It is therefore possible
to have a “next to” property as a pure topological property that is not grounded on
RCC8. We can define this different “next to” in the same way as we defined the origi-
nal OGC “touches” version, except that we cannot define it as a subproperty of the
geo:sf-touches property. In effect, the main difference is how we use it. But, we have
