xsd和xsi有什么区别？

What exactly is the difference between XML Schema Document and XML Schema Instance ?

XML Schema Document和XML Schema Instance之间究竟有什么区别？

• xmlns:xsd="http://www.w3.org/2001/XMLSchema"
• 的xmlns：XSD = “http://www.w3.org/2001/XMLSchema”
• xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
• 的xmlns：的xsi = “http://www.w3.org/2001/XMLSchema-instance”

Please elaborate.

请详细说明。

2 个解决方案

#1

xsd and xsi Similarities

• Both are XML namespace prefixes, abbreviations for an XML namespace.
• 两者都是XML名称空间前缀，XML名称空间的缩写。
• Both are, as are all namespace prefixes, arbitrarily named; other namespace prefix abbreviations could equally well be used. However, both prefixes are conventional and therefore recommended. (An also-conventional alternative to xsd is xs.)
• 正如所有命名空间前缀一样，两者都是任意命名的;同样可以使用其他名称空间前缀缩写。但是，这两个前缀都是传统的，因此建议使用。 （xsd的常规替代方案是xs。）

xsd and xsi Differences

• The xsd (or xs) prefix referring to the Schema Namespace (http://www.w3.org/2001/XMLSchema) is used in XML Schemas (XSDs) for the elements, attributes, and types of the W3C XML Schema Recommendation itself. (This is possible because XML Schema is itself XML.)
• 引用模式命名空间（http://www.w3.org/2001/XMLSchema）的xsd（或xs）前缀在XML模式（XSD）中用于W3C XML模式建议书本身的元素，属性和类型。 （这是可能的，因为XML Schema本身就是XML。）

• The xsi prefix referring to the The Schema Instance Namespace http://www.w3.org/2001/XMLSchema-instance is used in XML document instances for several special attributes defined by the XML Schema Recommendation:

  引用模式实例命名空间的xsi前缀http://www.w3.org/2001/XMLSchema-instance在XML文档实例中用于XML模式建议定义的几个特殊属性：

  • xsi:type allows an XML instance to associate element type information directly rather than through an XSD. See How to restrict the value of an XML element using xsi:type in XSD?

    xsi：type允许XML实例直接关联元素类型信息，而不是通过XSD。请参阅如何在XSD中使用xsi：type限制XML元素的值？

  • xsi:nil allows an empty element to be considered to be valid when the XSD might not otherwise have allowed it.

    xsi：nil允许在XSD可能不允许的情况下将空元素视为有效。

  • xsi:schemaLocation and xsi:noNamespaceSchemaLocation provide hints to the XML processor as to how to associate an XSD with an XML document. Use xsi:schemaLocation when there is a namespace; use xsi:noNamespaceSchemaLocation when there is no namespace.

    xsi：schemaLocation和xsi：noNamespaceSchemaLocation向XML处理器提供有关如何将XSD与XML文档关联的提示。有命名空间时使用xsi：schemaLocation;没有命名空间时使用xsi：noNamespaceSchemaLocation。

See Also

• Namespace related attributes in XML and XML Schema (XSD)
• XML和XML架构（XSD）中与命名空间相关的属性
• How to restrict the value of an XML element using xsi:type in XSD?
• 如何在XSD中使用xsi：type限制XML元素的值？

#2

http://www.w3.org/2001/XMLSchema

http://www.w3.org/2001/XMLSchema

The Simple Version : This is the namespace used within an XML Schema (XSD). An XML schema is used to describe what's valid within an XML instance document.

简单版本：这是XML Schema（XSD）中使用的命名空间。 XML模式用于描述XML实例文档中的有效内容。

The Less Simple Version : This is the namespace of an XML Schema that describes the structure of an XML Schema. In other words a schema that describes itself.

不太简单的版本：这是描述XML Schema结构的XML Schema的命名空间。换句话说，描述自己的模式。

An XML Schema (XSD) must be written using the types defined within this schema.

必须使用此模式中定义的类型编写XML模式（XSD）。

For Example.

例如。

<xs:schema elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
    <xs:element name="MyElement" type="xs:string" />
</xs:schema>

http://www.w3.org/2001/XMLSchema-instance

http://www.w3.org/2001/XMLSchema-instance

This is a namespace used within XML Instance documents to provide additional data to the XML Parser that is processing it. It describes the attributes xsi:schemalocation, xsi:noSchemalocation, xsi:type and xsi:nil which the XML parser can use to assist it with validation.

这是XML实例文档中使用的命名空间，用于向正在处理它的XML Parser提供其他数据。它描述了xsi：schemalocation，xsi：noSchemalocation，xsi：type和xsi：nil这些属性，XML解析器可以使用它来帮助验证。

For Example.

例如。

<MyElement xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
           xsi:noNamespaceSchemaLocation="MySchema.xsd">
    string
</MyElement>