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in the document <
http://example.criado.info/jones
> someone could write:
<#denise> fam:child <#edwin>, <smith#carol>.
or in RDF/XML:
<rdf:Description about="#denise"
<fam:child rdf:Resource="#edwin">
<fam:child rdf:Resource="http://example.criado.info/smith#
carol">
</rdf:Description>
Just with this we have a basic Semantic Web in the sense that the semantic data
are linked by the author of the contents. As a consideration it could be argued
that this model is an exact reflection of the traditional web pages, where the
authors of the contents decide the links.
Consideration 2
:
Embedded annotation
The current trend is to approach semantic annotation in an embedded way. Stan-
dards like HTML 5
3
,RDFa
4
and “XHTML+RDFa 1.1”
5
support this embedded
procedure, and implementations like Linkator[2], the adoption of ontologies like
GoodRelations
6
by Google
7
based on the use of “snippet” obviously confirm the
firmness of this W3C proposal.
However, embedded annotation has to solve the problem of guaranteeing the
coherence of the content that it represents. To explain this problem, the follow-
ing must be considered: firstly, we have to be able to do a semantic annotation,
i.e. formally represent a content, for example, of an HTML page in accordance
with one or several ontologies related to that content. Secondly, the actor that
uses or exploits this information now with semantics, for example, a search en-
gine, must be sure that the annotations that it processes are coherent with the
original content. If the annotation is embedded, then the HTML page incorpo-
rates semantics. What happens if something changes in the content affecting the
embedded annotation? What happens if something changes in the content not
affecting the embedded annotation? In both instances, if we calculate the HTML
file digital signature with a hash function, it is verified that the signature has
changed, so we can never be sure whether the “snippet” in RDFa representing
its semantic content in fact still matches the HTML page. There is no way of
guaranteeing coherence between content and annotation. In other words, be-
cause the annotation is inseparable from the HTML page the annotation update
is uncertain.
As a consideration, embedded annotation has the disadvantage of not being
able to guarantee coherence between the content and what has formally been
expressed in RDFa. Consequently, developing the Semantic Web in such a weak
model of inconsistency does not seem the most appropriate.
3
http://www.w3.org/TR/html5/
4
http://www.w3.org/TR/2010/WD-rdfa-core-20100803/
5
http://www.w3.org/TR/2010/WD-xhtml-rdfa-20100803/
6
http://www.heppnetz.de/projects/goodrelations/
7
http://www.google.com/support/webmasters/bin/answer.py?answer=186036
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