The RELATIONSHIP vocabulary can be used without modification with FOAF documents. Simply replace foaf:knows properties with a more specific property from this vocabulary. For backwards compatibility with older, non-RDF aware, tools, you may want to keep the foaf:knows property as well.
<rdf:RDF
xmlns:rdf=\"http://www.w3.org/1999/02/22-rdf-syntax-ns#\"
xmlns:rdfs=\"http://www.w3.org/2000/01/rdf-schema#\"
xmlns:foaf=\"http://xmlns.com/foaf/0.1/\"
xmlns:rel=\"http://purl.org/vocab/relationship/\"
>
<foaf:Person rdf:nodeID=\"ian\">
<foaf:name>Ian Davis</foaf:name>
<foaf:title>Mr</foaf:title>
<foaf:firstName>Ian</foaf:firstName>
<foaf:surname>Davis</foaf:surname>
<rel:hasMet>
<foaf:Person>
<foaf:name>William Tell</foaf:name>
</foaf:Person>
</rel:hasMet>
<rel:collaboratesWith rdf:nodeID=\"eric\"/>
</foaf:Person>
<foaf:Person rdf:nodeID=\"eric\">
<foaf:nick>pixel</foaf:nick>
</foaf:Person>
</rdf:RDF>
"""^^rdf:XMLLiteral .
The relationship vocabulary can be used to describe relationships with the people linked from a web page. This is particularly useful for blogrolls or contact lists but can be used with any type of link. The HTML a element provides two attributes, rel and rev, that can be used to specify the relationship. Both rel and rev take a space separated list of keywords as their value. To use a term from the relationship vocabulary just drop the http://purl.org/vocab/relationship/ namespace to leave the property name, e.g. http://purl.org/vocab/relationship/worksWith would become worksWith which can be added as the value of rel or rev.
rel
The rel attribute specifies a relationship that the author of the linked page has with the author of the linking page.
For example:
<ahref=\"http://example.com/boats\" rel=\"childOf\">The boat we restored\"</a>This link states that the author of http://example.com/boats is a child of the author of the html above.
rev
The rev attribute specifies a relationship that the author of the linking page has with the author of the linked page. The example here is:
<ahref=\"http://example.com/boats\" rev=\"childOf\">The boat we restored\"</a>In this case the meaning of the link is reversed: the author of the html above is a child of the author of http://example.com/boats.
The HTML and XHTML recommendations require an HTML document to declare a custom profile if it uses any non-standard rel or rev types. This is done by adding a profile attribute with a value of http://purl.org/vocab/relationship/ to the document's head element.
<head profile=\"http://purl.org/vocab/relationship/\">
<title>People I Know</title>
</head> <html profile=\"http://purl.org/vocab/relationship/\">
<head>
<title>People I Know</title>
</head>
<body>
<p>Here are the people I know:</p>
<ul>
<li><a href=\"http://example.com/~freddy\" rel=\"closeFriendOf\">Freddy (he's cool!)</a></li>
<li><a href=\"http://frooble.com/\" rel=\"mentorOf\">Jimbo</a></li>
<li><a href=\"http://mmmm.com/klm\" rel=\"friendOf\">Katie</a></li>
<li><a href=\"http://example.com/~omah\" rel=\"worksWith\">Omah (does the coding)</a></li>
<li><a href=\"http://example.com/~jason\" rev=\"closeFriendOf employedBy\">Jason, my henchman</a></li>
</ul>
</body>
</html>
Custom parsers that extract RDF from (X)HTML can use the relationships expressed in the links to infer the
equivilent RDF triples. It should be remembered that the relationship is between the authors of the pages not between
the pages themselves. Given the following link on a document at http://example.com/mypage.html:
<ahref=\"http://example.com/boats\" rel=\"childOf\">The boat we restored\"</a>a suggested RDF extraction is:
<foaf:Person>
<foaf:maker rdf:resource=\"http://example.com/boats\"/>
<rel:childOf>
<foaf:Person>
<foaf:maker rdf:resource=\"http://example.com/mypage.html\"/>
</foaf:Person>
</rel:childOf>
</foaf:Person>