XML Schema nillable=”true” vs minOccurs=”0″

出处：http://www.dimuthu.org/blog/2008/08/18/xml-schema-nillabletrue-vs-minoccurs0/
【前言】一个月前研究过nillable="true"和 vs minOccurs="0"的区分，没有想到啊，今天就记不得了，看来真是好记性不如烂笔头啊，况且我还么的好记性。。。。
【总结】英文一眼看不出结论，说点汉语直接些，别说我土哈~
nillable="true"：该元素的值可以为空，但是该元素不能省略，也就是说，只能：
<minzero xsi:nil="true"><minzero>
而不能直接将minzero这个元素去掉
（注意：xsi:nil="true"或者xsi:nil="1"应该就是表示这个元素为空）
minOccurs="0"：该元素可以直接被省略掉，但是不能让该元素的值为空，也就是说，不能：
<minzero xsi:nil="true"><minzero>
In a WSDL, XML Schema is the section where it define the message format for each operations, which eventually become the real API that users are interested. And it is the most tricky part of the WSDL. Nowadays there are many tools that you can design and use WSDLs without any needs in knowing the meaning of a single line of the WSDL. But there are situations that you may find it is better you have some knowledge in XML Schema section and in WSDL overall.
For this post I m taking a simple example of use of nillable=”true” and minOccurs=”0″. Take the following example.
<xs:element name="myelements">
<xs:complexType>
<xs:sequence>
<xs:element name="nonboth" type="xs:string"/>
<xs:element minOccurs="0" name="minzero" type="xs:int"/>
<xs:element name="nilint" nillable="true" type="xs:int"/>
<xs:element name="nilstring" nillable="true" type="xs:string"/>
<xs:element minOccurs="0" name="minzeronil" nillable="true" type="xs:string"/>
</xs:sequence>
</xs:complexType>
</xs:element>
Just ignore the meaning of what nillable and minOccurs attributes for now. You can safely say the following XML is valid for the above Schema.
<myelements>
<nonboth>i can't be either nil nor skipped<nonboth>