Database Reference
In-Depth Information
Ash Fleet Farm Te rrace
Ash Fleet Road
FIGURE 6.2
The Ash Fleet Farm Estate cottages.
and range to say that it refers to topographical objects only. Merea Maps uses the
term “near to” rather than “touches” not just so we can specify that it applies to
topographical objects but also because the term “touches” is not used in geography.
“next to” is special type of “touches” [geo].
“next to” must have the subject “Geographic Object”.
“next to” must have the object “Geographic Object”.
mm:nextTo rdfs:subpropertyOf geo:sf-touches.
mm:nextTo rdfs:domain mm:GeographicObject.
mm:nextTo rdfs:range mm:GeographicObject.
So, if we consider the row of terrace cottages (Figure 6.2) that are part of the Ash
Fleet Farm estate, we can say the following:
Rose Cottage is next to Bay Cottage.
mm:875483 mm:nextTo mm:875484.
Bay Cottage is next to Adder View.
mm:875484 mm:nextTo mm:875485.
and so on. MereaMaps can then define the other relations in a similar way. While we
have mentioned that topological properties offer the ability to provide reasoning, we
have not yet discussed an implementation of that reasoning; RDFS is not sufficiently
expressive to allow complex reasoning, but in Chapter 9 we describe the ontology
language OWL that will enable the properties to be more richly characterized.
By using the OGC Relations to explicitly state topological relationships between
features, we are able to use these properties to support queries using SPARQL.
However, as the properties are grounded in GeoSPARQL, they also enable us to infer
the topological properties of the features if there is geometry associated with them.
6.6.1.2 Non-RCC8 or OGC Topology
RCC8 and the OGC subset provide sets of topological properties that can provide
certainty in the relationships by being grounded in a well-defined geometry. The
problem for geography is that there is more to geography than just geometry. So,
while they are a good solution when geography is based on well-defined geometry,
