Database Reference
In-Depth Information
indexes within GIS. GI has matured in conjunction with the development of GIS,
and there have been spatial extensions to mainstream database products such as
Oracle, DB2, SQL Server, and MySQL. Most recently, the growth and usage of GI
have been affected by the implementation of Web-based tools such as Google Earth
and the creation of GI resources by volunteers, an example being OpenStreetMap,
a Web-based cartographic resource.
The use of GI has grown enormously, but many users will be largely unaware of
the role that GI plays in their activities. This is because GI is very rarely an end in
itself; rather, it normally forms the canvas on which the subject of interest is painted.
Thus, GI is present in a wide range of subject areas—ecology, land administra-
tion, town planning, insurance, marketing, and so on—but rarely as the main focus.
For something that is so obviously visual, it is therefore somewhat ironic that it is so
often unseen. Since there is a geographic context to so many subject areas, GI has
an important role to play in linking and combining datasets through shared loca-
tion. As yet, this potential for data integration based on GI is far from fully realized.
In part this is because the data itself is often not well organized; in part, it is because
the technology has not been there to aid the process.
1.2.2 t
he
S
emantic
W
eb
The World Wide Web had not yet been born during GI's formative years, while the
Semantic Web dates just to 1998 (Berners-Lee, 1998c) and so is barely in its teens. Here
in this introduction, we do not go into detailed explanations about the Semantic Web;
that is for further in the topic. For the moment, it is suficient to say that the Semantic
Web provides a means to describe, query, and reason over both data and Web con-
tent using a combination of established Web technologies such as HTTP (Hypertext
Transfer Protocol), a universal data structure (RDF, the Resource Description
Framework), a means to query that data (SPARQL), and a means to semantically
describe and annotate the data using ontologies (formal machine-readable descrip-
tions), usually expressed in RDFS (RDF Schema) or OWL (Web Ontology Language).
Linked Data, an integral and essential part of the Semantic Web, refers to a way
of publishing structured data on the Web (using RDF) and interlinking it. The notion
of Linked Data itself can be traced to the very origins of the Semantic Web; however,
the term
Linked Data
was only established later. Linked Data has been seen as sepa-
rate from the Semantic Web or even as the only part of the Semantic Web that works.
However, to us Linked Data is an integral part of the Semantic Web, and at the time
of writing, it was the most actively growing and developing element. Although at
times we do treat Linked Data on its own, if we do so it will be when Linked Data is
the particular focus, and when we do so, we always treat it
as a part of
the Semantic
Web. If we refer to the Semantic Web, we always do so in an inclusive manner with
respect to Linked Data.
1.3 GI IN THE SEMANTIC WEB
We believe that GI has certain aspects that require more careful consideration
when using it within the Semantic Web, but there is little if anything that is truly
