The Semantic Web - Social Semantics: The Search for Meaning on the Web - page 79

tag:redirectsHashTo property. The former models the TAG's 'solution' to
httpRange-14 while the latter represents the hash convention. With these kinds of
re-directions in hand, we can now model the typical Semantic Web transaction. A
new sub-class of URI , SemanticWebURI is given. A Semantic Web URI refers
to a resource that is not accessible on the Web such as the Eiffel Tower, and so the
URI must redirect to another URI that can access an information resource containing
data encoded in some Semantic Web language like RDF. Therefore, this kind of URI
also has a constraint that it must have at least one redirectsTo property.
As mentioned earlier, in the 'Linked Data Tutorial' note, the kinds of resources
referred to by a Semantic Web URI are called non-information resources (Bizer
et al. 2007). Although this term is controversial (and explicitly not endorsed
by Berners-Lee) and hard to define abstractly, operationally it simply means a
resource that is not web-accessible that therefore should, to comply with the Linked
Data initiative, use redirection to resolve to an information resource describing
the non-information resource. Although the space of non-information resources
is relatively large and hard to draw precise boundaries around, we list a few
exemplars in order to serve as what Dennett would call “intuition-pumps” in order
to help us understand this concept (Dennett 1981). In particular a new class called
ldow:NonInformationResource is introduced, which represents things that
cannot themselves - for whatever reason - be realized as a single digitally en-
coded message. Naturally, this class is disjoint with InformationResource .
A number of different kinds of things may be NonInformationResources .
Since this concept is the cause of much confusion and debate, it can obviously
range over physical people, artifacts, places, bodies, chemical substances, biological
entities, and the like - or to resources that are created in a social process and
cannot be completely realized digitally such as legal entities, political entities, social
relations, as well as the concept of a horse, and imaginary objects like unicorns or
even functions over the integers.
An associated description ( ldow:AssociatedDescription ) is an infor-
mation resource that can be accessed via redirection from a Semantic Web URI
(Bizer et al. 2007). In DBpedia 17 dbpedia:/resource/Eiffel Tower
redirects to dbpedia:/data/Eiffel Tower inRDF/XML,andtoanHTML
page at dbpedia:/page/Eiffel Tower depending on the requested media
type (Auer et al. 2007). This Linked Data typical scenario can be generalized
as follows: a WebClient requests a SemanticWebURI x and the re-
quest is redirected (via hash or 303 redirection) to another URI that identifies a
ldow:AssociatedDescription , which has one about property to a non-
information resource. The typical Linked Data terminology is represented in a
specific module of IRW referred to here by the prefix ldow: . 18 The associated
description is typically created in order to describe its associated non-information
resource. For an illustrated example of these classes in action, refer to Fig. 3.5 .
17 Prefix dbpedia: is used for the namespace http://dpedia.org .
18 http://ontologydesignpatterns.org/ont/web/ldow2irw.owl