A PI's data content tells the processor what we actually want it
to do. It is defined slightly differently in HTML and XML.
In XML, the data begins with the non-whitespace character
immediately after the target -- @see getTarget().
In HTML, the data begins with the character immediately after the
"<?" token that begins the PI.
Note that getNodeValue is aliased to getData
if (needsSyncData()) {
synchronizeData();
}
return data;