﻿<?xml version="1.0" encoding="UTF-8"?>
 <!--There is nothing special about XML. It is just plain text with
     the addition of some XML tags enclosed in angle brackets. In 
     other words, character data and markup. Character data is the 
     information that we are interested in. Markup records the 
     structure of the document.    
     Software that can handle plain text can also handle XML. In a
     simple text editor, the XML tags will be visible and will not
     be handled specially.
     In an XML-aware application however, the XML tags can be handled
     specially. The tags may or may not be visible, or have a  
     functional meaning, depending on the nature of the application. 
     -->
 <!--The first line in the document - the XML declaration - 
     defines the XML version and the character encoding used
     in the document. It must start on the first character of the
     first line of the document. In this case the document conforms to
     the 1.0 specification of XML and uses the UTF-8 character set.
     The declaration is not a part of the XML document itself. It 
     is not an XML element, and it should not have a closing tag.-->
 <!--The building block of the XML is the element. Each element has
     a name and a content. The content of the element is delimited by
     special markups known as start/opening tag and end/closing tag. 
     The start tag is the name of the element in angle brackets. The 
     end tag adds an extra slash character before the name.-->
 <!--Element names in XML must start with either a character or the
     underscore character "_". The rest of the name consists of letters
     , digits, "_"(underscore), "-"(hyphen), or "."(dot). Spaces are
     not allowed. Names cannot start with the string "xml", which is 
     reserved for the XML specification itself. ":"(colon) is allowed 
     in names and is reserved for namespaces. When a name consists of
     several word, the words are usually separated by a hyphen, as in
     address-book. Alternatively, the first letter of each word is 
     capitalised but use no separation character between the words,
     as in AddressBook. Whatever conventions you use, be consistent 
     and avoid the use of mix conventions.-->      
 <!--In XML all elements must have a closing tag. -->
 <!--XML tags are case sensitive. Opening and closing tags must
     therefore be written with the same case.-->
 <!--By convention, HTML elements in XML are always in uppercase.
     XML elements are frequently written in lowercase.-->
 <!--In XML all elements must be properly nested within each other.-->
 <!--All XML documents must contain a single tag pair to define a root
     element. All other elements must be within this root element.
     -->
 <!--The next line describes the root element of the document (like
     it was saying: "this document is a booklist")
     the last line defines the end of the root element.
     -->
<booklist>
 
 <!--All elements can have sub elements (child elements). Sub elements
     must be correctly nested within their parent element-->
 <book>
  <code>CODE</code>
  <title>TITLE</title>
  <authorlist>
    <author>AUTHOR</author>
  </authorlist>
  <price>PRICE</price>
 </book>
 <book>
  <code>F1</code>
  <title>文件1</title>
  <authorlist>
    <author>J S Lai</author>
    <author>A Kong</author>
    <author>Jac Lai</author>
  </authorlist>
  <price>HKD180</price>
 </book>	
 <book>
  <code>F2</code>
  <title>文件2</title>
  <authorlist>
    <author>Jac Lai</author>
  </authorlist>
  <price>USD180</price>	
 </book>
</booklist>
 <!--It is possible to attach additional information to elements in
     the form of attributes. Attributes have a name and a value.
     The names follow the same rules as element names. XML elements
     can have one or more attributes in the start tag. The name is 
     separated from the value by the equal character. The value must
     always be enclosed either in double or single quotation marks.
     This is convenient if you need to insert double or single 
     quotation marks in an attribute value. e.g.
     <confidentiality level='approved "for your eyes only"'>
     This document is not confidential.
     </confidentiality>
     -->
 <!--Empty elements are elements that have a name but no content.
     Usually, they are enclosed in the document for the value of 
     their attributes. e.g.
     <email href="mailto:jslai98@hotmail.com"></email>
     Alternatively, the start and end tags merge and the slash from
     the end tag is added at the end of the opening tag as follows:
     <email href="mailto:jslai98@hotmail.com"/>
     -->   
 <!--unlike HTML, With XML, the white space in your document is not
     truncated.-->
 <!--With XML, carriage return (CR) and line feed (LF) is converted
     to LF.--> 