Database Reference
In-Depth Information
mm:0012
http://mereabeers.co.me/sells
http://mereabeers.co.me/
OldBelcherBeer
http://mereabeers.co.me/is_brewed_in
http://sws.geonames.
org/2640726
FIGURE 5.2
RDF graph showing “The Isis Tavern sells Old Belcher Beer brewed in
Mereashire.”
exactly the same way. In
Table 5.3
, the URI of the object identifies the River Isis
from the well-known GeoNames RDF dataset. This is only possible in a relational
database if the table structure itself is changed; in RDF, we just add more data.
An RDF statement can only model a relationship between two things, such as between
the pub and the river. If we want to model how three or more things relate together, what
is known as an “
n
-ary relation,” for example to say, “The Isis Tavern sells Old Belcher
Beer brewed in Mereashire,” we need to introduce an intermediate resource. Let us pick
this example apart a bit more: We have the first statement, “The Isis Tavern sells Old
Belcher Beer,” and a second one that says: “Old Belcher Beer is brewed in Mereashire.”
In an RDF graph, this is fairly straightforward, as shown in Figure 5.2, where Old
Belcher Beer is represented as a class. So, the second statement says that every instance
of Old Belcher Beer, that is, every pint and every barrel, is brewed in Mereashire.
