Databases Reference
In-Depth Information
Structure of this chapter.
This chapter aims to explain the foundations of Linked Data
and introducing the di
ff
erent aspects of the Linked Data lifecycle by highlighting a par-
ticular approach and providing references to related work and further reading. We start
by briefly explaining the principles underlying the Linked Data paradigm in Section 2.
The first aspect of the Linked Data lifecycle is the extraction of information from un-
structured, semi-structured and structured sources and their representation according to
the RDF data model (Section 3). We present the user friendly authoring and manual
revision aspect of Linked Data with the example of Semantic Wikis in Section 4. The
interlinking aspect is tackled in Section 5 and gives an overview on the LIMES frame-
work. We describe how the instance data published and commonly found on the Data
Web can be enriched with higher level structures in Section 6. We present an overview
of the various data quality dimensions and metrics along with currently existing tools
for data quality assessment of Linked Data in Section 7. Due to space limitations we
omit a detailed discussion of the evolution as well as search, browsing and exploration
aspects of the Linked Data lifecycle in this chapter. The chapter is concluded by sev-
eral sections on promising applications of Linked Data and semantic technologies, in
particular Open Governmental Data, Semantic Business Intelligence and Statistical and
Economic Data.
Overall, this is an updated version of a similar lecture given at Reasoning Web Sum-
mer School 2011 [13].
2
The Linked Data Paradigm
In this section we introduce the basic principles of Linked Data. The section is partially
based on the Section 2 from [54]. The term Linked Data refers to a set of best practices
for publishing and interlinking structured data on the Web. These best practices were
introduced by Tim Berners-Lee in his Web architecture note Linked Data
1
and have
become known as the Linked Data principles. These principles are:
-
Use URIs as names for things.
-
Use HTTP URIs so that people can look up those names.
-
When someone looks up a URI, provide useful information, using the standards
(RDF, SPARQL).
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Include links to other URIs, so that they can discover more things.
The basic idea of Linked Data is to apply the general architecture of the World Wide
Web [71] to the task of sharing structured data on global scale. The Document Web
is built on the idea of setting hyperlinks between Web documents that may reside on
di
erent Web servers. It is built on a small set of simple standards: Uniform Resource
Identifiers (URIs) and their extension Internationalized Resource Identifiers (IRIs) as
globally unique identification mechanism [21], the Hypertext Transfer Protocol (HTTP)
as universal access mechanism [44], and the Hypertext Markup Language (HTML) as
a widely used content format [65]. Linked Data builds directly on Web architecture and
applies this architecture to the task of sharing data on global scale.
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