Database Reference
In-Depth Information
7.9.3 l
InkeD
D
ata
W
aIverS
A waiver is the opposite of a license: It allows data creators to unequivocally declare
that they do not want to assert legal rights to their data. To do this, the data creators
can simply state that their license is the Creative Commons Public Domain Waiver
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using the
dc:license
predicate. However, even though the publisher has waived
its rights, it may want to make sure that no one else can curtail the use of its data. One
vocabulary that can assist in doing this is the Waiver Vocabulary,
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which includes
a predicate
wv:norms
, allowing the data owner to indicate the expectations it has
about how its data will be used. This community norm is a nonbinding condition of
use that the publisher encourages users to abide by. One commonly used example
of this is the Open Data Commons Attribution Share Alike Norm (ODC-BY-SA),
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which asks that changes and updates to the dataset are made public, that the original
publisher is mentioned in the credits, that the source of the data is linked, that open
formats are used, and that no further digital rights management (DRM) is applied.
In the same way as the
dcterms:license
predicate is used to link the dataset to
its license, so can the
wv:norms
predicate be used to link a dataset to a community
norm specification.
7.10 SOFTWARE TOOLS
There are a number of commercially available and open source tools for storing
and publishing linked data. Many tools also come with a query engine and RDFS
inference. These include 3Store (a MySQL-based triple store from the University of
Southampton), which has been extended by a spin-off company into 4Store (which
is a database and query engine). Another option is the open source RDF database
Mulgara,
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which is written in Java with a SPARQL query engine.
There are a number of software frameworks (collections of tools and code libraries)
dealing with various aspects of Semantic Web processing and Linked Data, includ-
ing triple stores. For example, the Apache Jena Framework
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includes a Java API for
reading, processing, and writing RDF data in XML, N-triples, and Turtle formats;
an ontology API for handling OWL and RDFS ontologies; a rule-based inference
engine for reasoning with RDF and OWL data sources; an RDF triple store; and a
SPARQL query engine. Sesame,
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from Aduna Software, is another framework for
processing RDF data, including RDF storage, inferencing, and SPARQL querying.
It also offers transparent access to remote RDF repositories using the same API as
for local access.
Commercial choices include the Oracle 11g database,
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which uses its spatial
data model to store the RDF graph; Allegro Graph,
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which offers RDFS++ and
Prolog reasoning, with a specific geospatial datatype; BigData,
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which is an open
source distributed database that also offers limited OWL inference; and OpenLink
Virtuoso,
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which is a hybrid relational and RDF data store, along with a linked data
and Web application server.
However, the market is in flux, with new tools and features becoming available all
the time, so we cannot cover all the possible choices here.
