Determining relative path with jQuery

<span class="com">// Initiate asynchronous load of xml data:</span><span class="pln">
jQuery</span><span class="pun">.</span><span class="pln">ajax</span><span class="pun">({</span><span class="pln">
    type</span><span class="pun">:</span> <span class="str">"GET"</span><span class="pun">,</span><span class="pln">
    url</span><span class="pun">:</span> <span class="str">"/wp-content/themes/mytheme/data.xml"</span><span class="pun">,</span><span class="pln">
    dataType</span><span class="pun">:</span> <span class="str">"xml"</span><span class="pun">,</span><span class="pln">
    success</span><span class="pun">:</span><span class="pln"> parseDataXML
</span><span class="pun">});</span>