Label data – that is, descriptions of web resources using controlled vocabularies – may be available in a small file on the website itself, typically called labels.rdf, or it may come directly from the labelling authority. Either way, the labelled website will include a link to that data in the following format:
<link rel=”meta” href=”http://www.example.com/labels.rdf” type=”application/rdf+xml” />
The link tag may also include a title such as “ICRA labels.”
The data itself will be encoded using the RDF Content Labels system. This was developed under the Quatro project and provided significant impetus for work at the World Wide Web Consortium in this field, leading to the development of a new Protocol for Web Description Resources (POWDER).
Labelling Authorities will offer one or more methods by which a given label may be authenticated and may also make their full database available through various means as fits their business model. Participation in Quatro does not mandate that a particular approach and no other can be used. However, whatever other services they offer, LAs should set up a Data Access service, or DAcc, to work with the Quatro Proxy. This is a centralised service run by the Quatro partners that handles requests for labels for any given resource and authenticates the labels on request. See the Quatro proxy page for full details.