We have already seen a processing instruction. The XML declaration is a
processing instruction. And if you recall, when we introduced the XML
declaration we promised to return to the concept of processing instructions
to explain them as a category.
So here we are.
A processing instruction is a bit of information meant for the application using the XML
document. That is, they are not really of interest to the XML parser. Instead, the
instructions are passed intact straight to the application using the parser.
The application can then pass this on to another application or interpret it itself.
All processing instructions follow the generic format of
As you might imagine, you cannot use any combination of "xml" as the NAME_OF_APPLICATION_INSTRUCTION_IS_FOR
since "xml" is reserved. However, you might have something like:
<?JAVA_OBJECT JAR_FILE = "/java/myjar.jar"?>