The Header
The first
syntax we look at is XML itself. An XML document can be broken into
two basic pieces: the header, which gives an XML parser and XML
applications information about how to handle the document, and the
content, which is the XML data itself. Although this is a fairly
loose division, it will help us differentiate the instructions to
applications within an XML document from the XML content itself, and
is an important distinction to understand. In our example, we will
begin with the first several lines, which lead up to the
JavaXML:Book
element. These initial lines,
excluding the JavaXML:Book
element, make up the
document header. The term “header” is not a formal term
defined in the XML specification, but is commonly used in the XML
community, and we will use it in this book to denote these initial
lines of an XML document.
XML Instructions
The first statement you will see in any XML document is an XML
instruction. XML instructions are actually a
specific subset of processing instructions (PIs), which we talked
about in the last chapter. Remember that we said PIs are generally
passed on from the parser to the calling application, and handled
there. However, PIs that specify their target as
xml
are intended for the XML parser itself. They
specify the version of XML being used, a stylesheet, or other
information that a parser may need to know to properly parse XML
data. Here is an XML instruction:
<?xml version="1.0" standalone="no"?>
Like any other PI, it is of the form ...
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