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review of RDFa

From: lisa.seeman <lisa.seeman@zoho.com>
Date: Tue, 26 Aug 2014 14:34:54 +0300
To: "public-cognitive-a11y-tf" <public-cognitive-a11y-tf@w3.org>
Message-Id: <1481216d547.12a91b316143408.4654059939632141945@zoho.com>
 RDFa  (or Resource Description Framework in Attributes) is an extension to HTML5 that helps you markup more semantics in Web Content. Using RDFa, the author can annotate her page to make the structured data clear: 
 For example, one can say that this text is equivalent of a metadata title (a term defined at http://purl.org/dc/terms/title) as follows:
 &lt;h2 property="http://purl.org/dc/terms/title"&gt;The Trouble with Bob&lt;/h2&gt; &lt;p&gt;Date: &lt;span property="http://purl.org/dc/terms/created"&gt;2011-09-10&lt;/span&gt;&lt;/p&gt; See http://www.w3.org/TR/xhtml-rdfa-primer/diagrams/title-and-author.svg for a pictorial representation of the data. 
 Note thatyou can also define the vocab for the whole page making the attribute values simpler, as follows: 
 &lt;body vocab="http://purl.org/dc/terms/"&gt; ... &lt;h2 property="title"&gt;The Trouble with Bob&lt;/h2&gt; &lt;p&gt;Date: &lt;span property="created"&gt;2011-09-10&lt;/span&gt;&lt;/p&gt; The attributes in RDFa are:
 about – a URI specifying the resource the metadata is about
rel and rev – specifying a relationship and reverse-relationship with another resource, respectively
src, href and resource – specifying the partner resource
property – specifying a property for the content of an element or the partner resource
content – optional attribute that overrides the content of the element when using the property attribute
datatype – optional attribute that specifies the datatype of text specified for use with the property attribute
typeof – optional attribute that specifies the RDF type(s) of the subject or the partner resource (the resource that the metadata is about).
 Looking at the following example
 &lt;p&gt;My name is &lt;span property="foaf:nick"&gt;John D&lt;/span&gt; and I like &lt;a href="http://www.neubauten.org/" rel="foaf:interest" xml:lang="de"&gt;Einstürzende Neubauten&lt;/a&gt;. &lt;/p&gt; The RDFa terms are used to say what the element is, and how it is is relivent Any compliant vocablery can be link to to say this is an "X"
 Hence RDFa enables us to add more information to web pages without standardizing terms in HTML itself, and one can use vocabularies external to the W3C. For example authors could reference use terms defined or explained elsewhere, as symbols or, for example, terms defined by EPub (see http://www.idpf.org/epub/vocab/structure/)
 However RDFa can also be used t create a vocabularies (or you can use full RDF ). This is important because one can also add values to the ROLE attribute in HTML as HTML Role is modular. See http://www.w3.org/1999/xhtml/vocab
 Another use of RDFa for COGA would be to identify of alternative content for alternitive access strategies that exist in the same page. 
 Many RDFa vocabularies exist such as http://logd.tw.rpi.edu/datasets_rdfa, and http://schema.org/docs/schema_org_rdfa.html
 Currently RDFa does not seem to be used to improve accessibility for people with cognitive disabilities. No author strategies are defined to this aim. However it can act as an enabling technology for accessibility for people with cognitive disabilities allowing:
 alternative content
adaptable content
extra information.

All the best

Lisa Seeman

Athena ICT Accessibility Projects 
LinkedIn, Twitter
Received on Tuesday, 26 August 2014 11:37:29 UTC

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