Databases Reference
In-Depth Information
Fig. 3.
Example RDF graph containing 9 triples describing the city of Leipzig and its mayor
Problematic RDF features in the Linked Data Context.
Besides the features mentioned
above, the RDF Recommendation [1] also specifies some other features. In order to
make it easier for clients to consume data only the subset of the RDF data model de-
scribed above should be used. In particular, the following features are problematic when
publishing RDF as Linked Data:
-
RDF reification
(for making statements about statements) should be avoided if pos-
sible, as reified statements are rather cumbersome to query with the SPARQL query
language. In many cases using reification to publish metadata about individual RDF
statements can be avoided by attaching the respective metadata to the RDF docu-
ment containing the relevant triples.
-
RDF collections
and
RDF containers
are also problematic if the data needs to be
queried with SPARQL. Therefore, in cases where the relative ordering of items
in a set is not significant, the use of multiple triples with the same predicate is
recommended.
-
The scope of
blank nodes
is limited to the document in which they appear, meaning
it is not possible to create links to them from external documents. In addition, it
is more di
erent sources when blank nodes are used,
as there is no URI to serve as a common key. Therefore, all resources in a data set
should be named using IRI references.
cult to merge data from di
ff
2.4
RDF Serializations
The initial o
cial W3C RDF standard [1] comprised a serialization of the RDF data
model in XML called
RDF
XML
. Its rationale was to integrate RDF with the existing
XML standard, so it could be used smoothly in conjunction with the existing XML
technology landscape. Unfortunately, RDF
/
cult to un-
derstand for the majority of potential users, since it requires to be familiar with two
data models (i.e. the tree-oriented XML data model as well as the statement oriented
RDF datamodel) and interactions between them, since RDF statements are represented
in XML. As a consequence, with
N-Triples
,
Turtle
and
N3
a family of alternative
/
XML turned out to be rather di
