XSD key/keyref 初学者问题 [英] XSD key/keyref beginner question

问题描述

我正在尝试实现一个非常简单的 XML 模式约束.

I'm trying to implement a very simple XML schema constraint.

idref 元素的属性类型 <batz> 只能是允许有一个匹配的值至少一个上的 id 属性元素<bar>.

The idref attribute on elements of type <batz> should only be allowed to have a value that matches the id attribute on at least one element <bar>.

如果这对您没有任何意义，那么请看下面的示例 XML 文档，我认为它实际上比我试图用文字来解释它更好.

If that doesn't make any sense to you then please just look at the example XML-document below, I think it actually explains it better than my attempt to put it in words.

那么，问题:为什么 xmllint 让下面的 schema/xml 组合通过(它说文档是有效的)?如何修复它以实现所需的约束?

So, question: Why does xmllint let the below schema/xml combination pass (it says the document is valid)? How to fix it to achieve the desired constraint?

架构:

<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
    targetNamespace="test" xmlns="test" elementFormDefault="qualified">

    <xs:element name="foo">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="bar" minOccurs="0" maxOccurs="unbounded">
                    <xs:complexType>
                        <xs:attribute name="id" use="required" type="xs:string" />
                    </xs:complexType>
                </xs:element>
                <xs:element name="batz" minOccurs="0" maxOccurs="unbounded">
                    <xs:complexType>
                        <xs:attribute name="idref" use="required" type="xs:string" />
                    </xs:complexType>
                </xs:element>
            </xs:sequence>
        </xs:complexType>

        <xs:key name="ID">
            <xs:selector xpath="./bar" />
            <xs:field xpath="@id" />
        </xs:key>

        <xs:keyref name="IDREF" refer="ID">
            <xs:selector xpath="./batz" />
            <xs:field xpath="@idref" />
        </xs:keyref>

    </xs:element>
</xs:schema>

文件:

<?xml version="1.0"?>
<foo xmlns="test">
    <bar id="1" />
    <bar id="2" />
    <batz idref="1" /> <!-- this should succeed because <bar id="1"> exists -->
    <batz idref="3" /> <!-- this should FAIL -->
</foo>

推荐答案

如图所示，您的 XML 文档不包含 schemaLocation.当 XML 文档不引用模式或 DTD 时，它可以通过格式正确的 XML 简单地通过验证.(这曾经发生在一位同事身上，使用了不同的验证器.我认为这是一个错误，验证器至少没有给出缺少架构或 DTD 的警告.但我离题了.)

Your XML document, as shown, doesn't include a schemaLocation. When an XML document doesn't reference a schema or DTD, it may pass validation simply by being well-formed XML. (This once happened to a co-worker, using a different validator. I think it's a bug that the validator didn't at least give a warning that it was missing a schema or DTD. But I digress.)

不管怎样，应该是这样的:

Anyway, it should probably be something like:

<?xml version="1.0"?>
<foo
  xmlns="test" <!-- This is bad form, by the way... -->
  xsi:schemaLocation="test /path/to/schema/document"
    <bar id="1" />
    <bar id="2" />
    <batz idref="1" /> <!-- this should succeed because <bar id="1"> exists -->
    <batz idref="3" /> <!-- this should FAIL -->
</foo>

这篇关于XSD key/keyref 初学者问题的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！