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RDF (Resource Description Framework) provides a way for applications to automatically exchange and understand information. RDF uses XML to define a framework for processing metadata, making it possible for search engines and Web content providers to automatically understand such things as "title," "author" and "format." Without RDF, software applications would have to know specifically how such information is structured on each Web site to tap in to the data automatically.
XML (eXtensible Markup Language) is a more sophisticated markup language than HTML and it makes it possible to use RDF to express quite complex metadata structures. XML provides the encoding syntax, and the XML-namespace facility makes it straightforward to mix element sets in a given metadata description without the danger of element names colliding. That is, an element established as a component of one namespace, such as the Dublin Core, is in no danger of being confused with an element of the same name from another namespace.
Case is significant in XML, so 'dc'means something different to 'DC'.
In order to adhere to the Dublin Core recommendation, metadata elements are to be described using lower-case only, i.e. 'dc'not 'DC'. This only affects the way metadata is written in RDF, not in HTML.
Qualified metadata looks somewhat different (from its HTML appearance) when written in RDF. One significant difference is that the dot (.) notation used for expressing element qualifiers is not used in RDF. The other obvious feature of RDF is the declaration of the schemas being used in XML-namespace (xmlns) at the top of the metadata record.
Metadata expressed in XML/RDF is stored separately from the resource being described (i.e. is not embedded in the <HEAD> of a document).
[Please note that the way in which metadata is expressed in XML/RDF may change from the following examples]
XML/RDF Examples:
<?xml version="1.0"?>
<RDF:RDF xmlns:RDF="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:DC="http://purl.org.metadta/dublin_core#">
<RDF:Description RDF:about="http://oasis.gov.ie/housing/general/paying_for_a_home.html">
<DC:Contributor RDF:value="None"/>
<DC:Coverage RDF:value="Ireland"/>
<DC:Creator RDF:value="OASIS Project"/>
<DC:Date.Created RDF:value="2001-01-29" scheme="ISO8601"/>
<DC:Description RDF:value="Loans for buying a home are available from building societies,
banks, and local authorities. There are different kinds of mortgages, and tax relief
is available on interest payments."/>
<DC:Format RDF:value="text/xml"/>
<DC:Identifier RDF:value="http://oasis.gov.ie/housing/general/paying_for_a_home.html" scheme="URI"/>
<DC:Language RDF:value="en"/>
<DC:Publisher RDF:value="OASIS Project"/>
<DC:Rights RDF:value="© Government of Ireland 2001"/>
<DC:Source>
<RDF:bag
RDF:_1="CIDB: types of mortgage and choosing a mortgage A01034"
RDF:_2="01017"/>
</DC:Source>
<DC:Subject>
<RDF:bag
RDF:_1="house purchase;"
RDF:_2="mortgages"
RDF:_3="housing finance"/>
</DC:Subject>
<DC:Title RDF:value="Paying for a home"/>
<DC:Type RDF:value="OASIS services document"/>
</RDF:Description>
</RDF:RDF>
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<?xml version="1.0"?> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:dcq=http://purl.org/dc/qualifiers/1.0/> <rdf:Description rdf:about="http://oasis.gov.ie/housing/general/paying_for_a_home.html"> <dc:identifier>http://oasis.gov.ie/housing/general/paying_for_a_home.html</dc:identifier> <dc:creator xml:lang="en"> <dc:publisher xml:lang="en"> <dc:rights> <dc:title xml:lang="en">Paying for a Home</dc:title> <dc:subject> <dc:description xml:lang="en">Loans for buying a home are available from building societies, banks, and local authorities. There are different kinds of mortgages, and tax relief is available on interest payments</dc:description> <dc:language> <dc:coverage xml:lang="en"> <dc:date> <dc:type xml:lang="en">life event document</dc:type> <dc:format> </rdf:Description> </rdf:RDF> |