RewriteEngine on
RewriteBase /{farm}

RewriteCond %{REQUEST_URI} ^/?$
RewriteRule .* {farmer} [QSA,R,L]

RewriteCond %{REQUEST_URI} !^{farmer}?
RewriteCond %{REQUEST_URI} !^{barn}?
RewriteCond %{REQUEST_URI} !^farm.wsdl
RewriteRule (.*) {barn}$1 [QSA,L]