XSD: key and keyref validation

问题

I'm having issues with schema validation, this is my xml

<?xml version="1.0" encoding="utf-8" ?>
<root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:noNamespaceSchemaLocation='favorites.xsd'>
    <Favorites>
        <Folder>
            <Name>Entertainment</Name>
            <Bookmarks>
                <Bookmark ID="1"/>
                <Bookmark ID="200"/> <!-- This should fail validation -->
            </Bookmarks>
        </Folder>
    </Favorites>
    <Bookmarks>
        <Bookmark>
            <ID>1</ID>
            <URL>www.website1.com</URL>
        </Bookmark>
        <Bookmark>
            <ID>2</ID>
            <URL>www.website2.com</URL>
        </Bookmark>
        <Bookmark>
            <ID>3</ID>
            <URL>www.website3.com</URL>
        </Bookmark>
    </Bookmarks>
</root>

The ID element in Bookmark should be the key, and the Favorites/Folder/Bookmarks/Bookmark ID attribute should always reference a Bookmark ID.

Here is my xsd:

<?xml version="1.0"?>
<xs:schema xmlns:xs='http://www.w3.org/2001/XMLSchema'>
    <xs:element name="root">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="Favorites" type="Favorites"/>
                <xs:element name="Bookmarks" type="Bookmarks"/>
            </xs:sequence>
        </xs:complexType>
        <xs:keyref name="bookmarkIDKeyRef" refer="bookmarkIDKey">
            <xs:selector xpath="root/Favorites/Folder/Bookmarks/*"/>
            <xs:field xpath="@ID"/>
        </xs:keyref>
        <xs:key name="bookmarkIDKey">
            <xs:selector xpath="root/Bookmarks/Bookmark/ID"/>
            <xs:field xpath="ID"/>
        </xs:key>
    </xs:element>

    <xs:complexType name="Favorites">
        <xs:sequence maxOccurs="unbounded">
            <xs:element name="Folder" type="Folder"/>
        </xs:sequence>
    </xs:complexType>

    <xs:complexType name="Folder">
        <xs:sequence>
            <xs:element name="Name" type="xs:string"/>
            <xs:element name="Bookmarks">
                <xs:complexType>
                    <xs:sequence maxOccurs="unbounded">
                        <xs:element name="Bookmark">
                            <xs:complexType>
                                <xs:attribute name="ID" type="xs:string"/>
                            </xs:complexType>
                        </xs:element>
                    </xs:sequence>
                </xs:complexType>
            </xs:element>
        </xs:sequence>
    </xs:complexType>

    <xs:complexType name="Bookmarks">
        <xs:sequence maxOccurs ="unbounded">
            <xs:element name="Bookmark" type="Bookmark"/>
        </xs:sequence>
    </xs:complexType>

    <xs:complexType name="Bookmark">
        <xs:sequence>
            <xs:element name="ID" type="xs:string"/>
            <xs:element name="URL" type ="xs:string"/>
        </xs:sequence>
    </xs:complexType>

</xs:schema>

The xml is well formed, but the validation on the ID attribute is not working.

回答1:

The context of your keys is the <root> element, because in the schema they are children of the <xs:element name="root"> element. Therefore your <xs:selector> XPaths fail, because they begin with root/... which is not a child of the <root> element. Drop it for both key and keyref. Also the <xs:field> of the key fails due to similar issue. You already select the <ID> element as the context and then try to look for an <ID> child for this element. Switch the XPath of the <xs:field> to . (a dot) or drop the trailing /ID from the selector.

Here is a working code sample.

<xs:element name="root">
    <xs:complexType>
        <xs:sequence>
            <xs:element name="Favorites" type="Favorites"/>
            <xs:element name="Bookmarks" type="Bookmarks"/>
        </xs:sequence>
    </xs:complexType>
    <xs:keyref name="bookmarkIDKeyRef" refer="bookmarkIDKey">
        <xs:selector xpath="Favorites/Folder/Bookmarks/*"/>
        <xs:field xpath="@ID"/>
    </xs:keyref>
    <xs:key name="bookmarkIDKey">
        <xs:selector xpath="Bookmarks/Bookmark"/>
        <xs:field xpath="ID"/>
    </xs:key>
</xs:element>

来源：https://stackoverflow.com/questions/8273312/xsd-key-and-keyref-validation