XML 架构: maxOccurs ， minOccurs [英] XML-Schema : maxOccurs , minOccurs

问题描述

当我运行我的代码时，它给了我这个错误

When I run my code it gives me this error

[ s4s-att-not-allowed: Attribute 'maxOccurs' cannot appear in element 'element'.]

这是我的架构:

<xs:element name="parameters" maxOccurs="1" minOccurs="0">
    <xs:complexType>
        <xs:all>
            <xs:element ref="p ?"/> 
        </xs:all>
    </xs:complexType>
</xs:element>

推荐答案

可以在顶层声明(低于 xs:schema)但它不能有 minOccurs 或 maxOccurs 因为没有上下文就没有任何意义.如果它是根元素，则它只能有一个元素，如果不是，则该信息指的是父元素的上下文.这是合法的:

<xs:element> may be declared at top-level (below xs:schema) but it can't have minOccurs or maxOccurs since that doesn't make any sense without a context. If it's root it can only have one element, if it's not, that information refers to the context of the parent element. This is legal:

<xs:schema ...>
    <xs:element name="parameters">...</xs:element>
    ...
</xs:schema>

但这不是:

<xs:schema ...>
    <xs:element name="parameters" maxOccurs="1" minOccurs="0">...</xs:element>
...
</xs:schema>

您可以引用到一个组中的顶级xs:element，例如xs:sequence.在这里，您可以使用这些属性，因为现在您有了一个上下文(该组中允许有多少个).这是合法的:

You can refer to a top level xs:element within a group such as xs:sequence. Here you can use these attributes because now you have a context (how many are allowed in this group). This is legal:

<xs:schema ...>
    <xs:element name="parent">
        <xs:complexType>
            <xs:sequence>
                 <xs:element ref="parameters" maxOccurs="1" minOccurs="0" />
            </xs:sequence>
        </xs:complexType>
    </xs:element>

    <xs:element name="parameters">
        <xs:complexType>
            <xs:all>
                <xs:element ref="p" minOccurs="0"/> 
            </xs:all>
        </xs:complexType>
    </xs:element>
    ...
</xs:schema>

这里的 是 出现的上下文，所以你可以说它允许在那里出现多少次. 的定义是全局的，您可以使用 ref 属性来引用它.

Here <parent> is the context where <parameters> occurs, so you can say how many times it's allowed in there. The definition of <parameters> is global and you use the ref attribute to refer to it.

如果你永远不需要重用 parameters 或者如果你永远不会将 parameters 作为 root，你不需要它在顶层并且可以嵌套它在您的 parent 定义中.在这种情况下，您可以将 name 属性与 minOccurs 和 maxOccurs 一起使用.

If you never need to reuse parameters or if you are never going to have parameters as root, you don't need it at top-level and can nest it inside your parent definition. In this case you can use the name attribute with minOccurs and maxOccurs.

<xs:schema ...>
    <xs:element name="parent">
        <xs:complexType>
            <xs:sequence>
                 <xs:element name="parameters" maxOccurs="1" minOccurs="0" />
                     <xs:complexType>
                          <xs:all>
                               <xs:element ref="p" minOccurs="0"/> 
                          </xs:all>
                     </xs:complexType>
                 </xs:element>
            </xs:sequence>
        </xs:complexType>
    </xs:element>

    ...
</xs:schema>

您也可以引用顶级类型.重用、扩展和限制类型更为常见，因此这也是定义元素的有效(且推荐)方式:

You can also refer to a top-level type. It's more common to reuse, extend and restrict types, so this is also a valid (and recommended) way to define your element:

<xs:schema ...>
    <xs:element name="parent">
        <xs:complexType>
            <xs:sequence>
                 <xs:element name="parameters" type="ParameterType" maxOccurs="1" minOccurs="0" />
            </xs:sequence>
        </xs:complexType>
    </xs:element>

    <xs:complexType name="ParameterType">
        <xs:all>
            <xs:element ref="p" minOccurs="0"/> 
        </xs:all>
    </xs:complexType>
    ...
</xs:schema>

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