content negotiation in .htaccess to serve an RDF voc as HTML or rdf+xml depending on the client request

.htaccess for RDF voc

# Turn off MultiViews
Options -MultiViews

# Directive to ensure *.rdf files served as appropriate content type,
# if not present in main apache config
AddType application/rdf+xml .rdf

# Rewrite engine setup
RewriteEngine On
RewriteBase /irc/2008/09/25

# Rewrite rule to serve HTML content from the vocabulary URI if requested
RewriteCond %{HTTP_ACCEPT} !application/rdf\+xml.*(text/html|application/xhtml\+xml)
RewriteCond %{HTTP_ACCEPT} text/html [OR]
RewriteCond %{HTTP_ACCEPT} application/xhtml\+xml [OR]
RewriteCond %{HTTP_USER_AGENT} ^Mozilla/.*
RewriteRule ^voc$ voc.html [R=303]

# Rewrite rule to serve RDF/XML content from the vocabulary URI if requested
RewriteCond %{HTTP_ACCEPT} application/rdf\+xml
RewriteRule ^voc$ voc.rdf [R=303]

# Default response : Rewrite rule to serve the RDF/XML content from the vocabulary URI by default
RewriteRule ^voc$ voc.rdf [R=303]