XML 架构如何通过枚举限制属性

我有以下 XML 标记

<price currency="euros">20000.00</price>

如何将 currency 属性限制为以下属性之一:

  • 欧元
  • 英镑
  • 美元

双倍的价钱呢？

当我在两个类型上都尝试一个类型时，我得到了一个错误，以下是我目前得到的:

<xs:element name="price">
<xs:complexType>
<xs:attribute name="currency">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="pounds" />
<xs:enumeration value="euros" />
<xs:enumeration value="dollars" />
</xs:restriction>
</xs:simpleType>
</xs:attribute>
</xs:complexType>
</xs:element>
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you need to create a type and make the attribute of that type: 

<xs:simpleType name="curr">
<xs:restriction base="xs:string">
<xs:enumeration value="pounds" />
<xs:enumeration value="euros" />
<xs:enumeration value="dollars" />
</xs:restriction>
</xs:simpleType>

then: 

<xs:complexType>
<xs:attribute name="currency" type="curr"/>
</xs:complexType>
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最佳答案

The numerical value seems to be missing from your price definition. Try the following:

<xs:simpleType name="curr">
<xs:restriction base="xs:string">
<xs:enumeration value="pounds" />
<xs:enumeration value="euros" />
<xs:enumeration value="dollars" />
</xs:restriction>
</xs:simpleType>






<xs:element name="price">
<xs:complexType>
<xs:extension base="xs:decimal">
<xs:attribute name="currency" type="curr"/>
</xs:extension>
</xs:complexType>
</xs:element>
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New answer to old question

None of the existing answers to this old question address the real problem.

The real problem was that xs:complexType cannot directly have a xs:extension as a child in XSD. The fix is to use xs:simpleContent first. Details follow...

Your XML,

<price currency="euros">20000.00</price>

will be valid against either of the following corrected XSDs:

Locally defined attribute type

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">


<xs:element name="price">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:decimal">
<xs:attribute name="currency">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="pounds" />
<xs:enumeration value="euros" />
<xs:enumeration value="dollars" />
</xs:restriction>
</xs:simpleType>
</xs:attribute>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
</xs:schema>

Globally defined attribute type

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">


<xs:simpleType name="currencyType">
<xs:restriction base="xs:string">
<xs:enumeration value="pounds" />
<xs:enumeration value="euros" />
<xs:enumeration value="dollars" />
</xs:restriction>
</xs:simpleType>


<xs:element name="price">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:decimal">
<xs:attribute name="currency" type="currencyType"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
</xs:schema>

Notes

  • As commented by @Paul, these do change the content type of price from xs:string to xs:decimal, but this is not strictly necessary and was not the real problem.
  • As answered by @user998692, you could separate out the definition of currency, and you could change to xs:decimal, but this too was not the real problem.

The real problem was that xs:complexType cannot directly have a xs:extension as a child in XSD; xs:simpleContent is needed first.

A related matter (that wasn't asked but may have confused other answers):

How could price be restricted given that it has an attribute?

In this case, a separate, global definition of priceType would be needed; it is not possible to do this with only local type definitions.

How to restrict element content when element has attribute

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">


<xs:simpleType name="priceType">
<xs:restriction base="xs:decimal">
<xs:minInclusive value="0.00"/>
<xs:maxInclusive value="99999.99"/>
</xs:restriction>
</xs:simpleType>


<xs:element name="price">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="priceType">
<xs:attribute name="currency">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="pounds" />
<xs:enumeration value="euros" />
<xs:enumeration value="dollars" />
</xs:restriction>
</xs:simpleType>
</xs:attribute>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
</xs:schema>

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