The Semantic Web - Social Semantics: The Search for Meaning on the Web - page 67

for the homepage of the Eiffel Tower. When this URI returns the 200 status code in
response to an HTTP GET request, the agent can infer that the homepage is actually
an information resource. The Semantic Web URI used to refer to the Eiffel Tower
itself, http://www.example.org/EiffelTower , could be any kind of resource, and so
could be a Semantic Web resource. This 303 redirection then allows the Semantic
Web resource given by a Semantic Web URI for the Eiffel Tower itself to comply
with the Principle of Self-Description.
An alternative to the obtuse 303 redirection is the hash convention , where one
uses the fragment identifier of a URI to get redirection for free. If one wanted a
Semantic Web URI that referred to a non-information resource like the Eiffel Tower
itself without the hassle of a 303 redirection, one would use the URI http://www.
tour-eiffel.fr/# to refer to the Eiffel Tower itself. Since browsers, following the
follow-your-nose algorithm, either dispose of it or treat the fragment identifier as a
fragment of a document or some other Web representation, if an agent tries to access
via HTTP GET a Semantic Web URI that uses the hash convention, the server will
not return a 404 Not Found status code, but instead resolve to the URI before the
hash, http://www.tour-eiffel , which can then be treated as a documentation resource.
In this way, Semantic Web inference engines can keep the Semantic Web URI that
refers to the Eiffel Tower itself and an associated description about the Eiffel Tower
separate by taking advantage of some predefined behaviour in web browsers.
While at first these distinctions between Semantic Web resources and informa-
tion resources seems ludicrously fine-grained, clarifying them and pronouncing an
official W3C policy on them had an immense impact on the Semantic Web, since
once there was definite guidelines on how to publish information on the Semantic
Web, users could start creating Semantic Web URIs and connecting them to relevant
documentation resources. The TAG's decision on redirection was made part of a
tutorial for publishing Semantic Web information called How to Publish Linked
Data on the Web (Bizer et al. 2007).

3.4 An Ontology of Web Architecture

The primary use of a formal ontology in the context of Web architecture is to allow
us to formally model the various distinctions used in specifications and debates.
Although some other formal logic that deals with actions and events may be more
suitable for modelling the temporal transactions of client-server interactions on the
Web, an ontology is necessary in order to capture the various distinctions given
in specifications first. As even the primary architects of the Web find themselves
confused about the distinctions between 'entities' in HTTP and 'representations'
in Web architecture (Mogul 2002), this ontology could be of use as a reference to
anyone interested in understanding or even extending existing Web specifications as
well as those interested in correctly implementing best practices that are dependent
on rather obscure corners of Web architecture, such as Linked Data's 303 redirects.
A first attempt to formally model Web concepts was the Identity, Resources, and