Database Reference
In-Depth Information
L3 to L4
L2 to L3
L3
L2
L1 to L2
L4
L1
L6
L5
L5 to L6
L4 to L5
FIGURE 3.4
Building footprint represented as a polygon constructed from multiple lines.
occurring, care must be taken not to confuse topology and mereology. Consider the
following: An English county is an administrative unit that wholly contains a num-
ber of boroughs or districts, which are also administrative areas. We can certainly
say that topologically a district is “contained within” a county. But it is only valid
to say that a borough is “part of” a county if there is some formal relationship that
makes a borough a functional part of a county. It turns out that this is not the case;
essentially, a borough shares an area of land with a county, but each operates inde-
pendently and has a different administrative role. As we shall see further in this
topic, the process of describing such objects for the Semantic Web can often tease
out such subtleties.
As we will see, both topology and mereology have important roles to play when
expressing GI in Linked Data terms.
3.3.3 t
Textual
r
epresentations
We are all familiar with textual representations of GI, although we are so familiar
with these forms that we tend not to think about them as representations of GI.
There are at least four types of such textual representations: description, classifica-
tion, direction, and address.
3.3.3.1 Description
Textual descriptions are quite simply that: descriptions of the landscape, place, or
other geographical feature. Here is a typical example that is simply littered with
geographical references:
As Barry, Jane and I walked up the track across the heath to our old campsite, we
passed Gentian Valley, and, reassuringly, the deep blue marsh gentians were still there,
in flower, half hidden in the heather. But gorse had taken over the campsite hollow,
