1. 简介

what is a xml schema language?

什么是 xml schema 语言？

i will insist more on this point during my comparison of xml schema languages on wednesday morning, but one thing is sure: a xml schema language is probably not what you're expecting, and its main feature is not (or not always) to describe a class of xml documents but rather to act as a filter or firewall to protect applications from the wide diversity of well formed xml documents.

我将在星期三早上对各种 xml schema 语言进行比较的时候会强调更多事情，但是一件事情是肯定的：一种 xml schema 语言可能不是你所期望的，但是它的主要特性不是（或者不总是）去描述一类 xml 文档而是作为一个过滤器或者防火墙来把程序从各种各样合式的 xml 文档保护起来。

all over this tutorial we will use the following example:

整个教程我将使用这个例子：

 <?xml version="1.0"?>
 <library>
  <book id="_0836217462">
    <isbn>
      0836217462
    </isbn>
    <title>
      being a dog is a full-time job
    </title>
    <author-ref id="charles-m.-schulz"/>
    <character-ref id="peppermint-patty"/>
    <character-ref id="snoopy"/>
    <character-ref id="schroeder"/>
    <character-ref id="lucy"/>
  </book>
  <book id="_0805033106">
    <isbn>
      0805033106
    </isbn>
    <title>
      peanuts every sunday
    </title>
    <author-ref id="charles-m.-schulz"/>
    <character-ref id="sally-brown"/>
    <character-ref id="snoopy"/>
    <character-ref id="linus"/>
    <character-ref id="snoopy"/>
  </book>
  <author id="charles-m.-schulz">
    <name>
      charles m. schulz
    </name>
    <nickname>
      sparky
    </nickname>
    <born>
      1992-11-26
    </born>
    <dead>
      2000-02-12
    </dead>
  </author>
  <character id="peppermint-patty">
    <name>
      peppermint patty
    </name>
    <since>
      1966-08-22
    </since>
    <qualification>
      bold, brash and tomboyish
    </qualification>
  </character>
  <character id="snoopy">
    <name>
      snoopy
    </name>
    <since>
      1950-10-04
    </since>
    <qualification>
      extroverted beagle
    </qualification>
  </character>
  <character id="schroeder">
    <name>
      schroeder
    </name>
    <since>
      1951-05-30
    </since>
    <qualification>
      brought classical music to the peanuts strip
    </qualification>
  </character>
  <character id="lucy">
    <name>
      lucy
    </name>
    <since>
      1952-03-03
    </since>
    <qualification>
      bossy, crabby and selfish
    </qualification>
  </character>
  <character id="sally-brown">
    <name>
      sally brown
    </name>
    <since>
      1960-08-22
    </since>
    <qualification>
      always looks for the easy way out
    </qualification>
  </character>
  <character id="linus">
    <name>
      linus
    </name>
    <since>
      1952-09-19
    </since>
    <qualification>
      the intellectual of the gang
    </qualification>
  </character>