I'm currently doing the following but it feels "kludgy":

module Sinatra
    module DynFormat
        def dform(data,ct)
            if ct == 'xml';return data.to_xml;end
            if ct == 'json';return data.to_json;end
        end
    end
    helpers DynFormat
end

My goal is to plan ahead. Right now we're only working with XML for this particular web service but we want to move over to JSON as soon as all the components in our stack support it.

Here's a sample route:

get '/api/people/named/:name/:format' do
    format = params[:format]
    h = {'xml' => 'text/xml','json' => 'application/json'}
    content_type h[format], :charset => 'utf-8'
    person = params[:name]
    salesperson = Salespeople.find(:all, :conditions => ['name LIKE ?', "%#{person}%"])
    "#{dform(salesperson,format)}"
end

It just feels like I'm not doing it the best way possible.