processing instructions

A processing instruction contains information that is passed from the XML document to the document parser. This means, of course, that a parser must contain special code to generate a proper response to the processing instructions that it will encounter.

A processing instruction begins with <? and ends with ?>. The ModelTools schema uses one processing instruction: include. This processing instruction is used to include a file into the XML document at the position of the processing instruction.


<?include MyNearbyFile ?>

The include file names are relative to the location of the include processing instruction. This means that a simple file name can typically be used. The parser's file manager keeps up with the other requisite details.

XML declaration

There is also a processing instruction like element called the XML declaration that details the version of XML that is being used. For example

<?xml version=1.0' ?>

The XML declaration should be the first element in the document. But it is optional and in this schema it is honored wherever it is and then it is ignored.