Constraints for nested elements; key and keyref

[ea_6666@freenet.de]

Hi all,

i have a question about constraints, in detail about nested constraints.

I have several elements named 'parent' with an attribute named 'parentid' and subelements 'child' also 
with an attribute 'childid'. My intention (first part) is that each child is unique with respect to the childid 
in his parent and each parent is unique with respect to his parentid in the root element. This can be done 
by the two keys 'childKey' and 'parentKey'.
The second part of my intention is to reference in an later section of the xml-file to the childs, like it is show below.
The problem is to describe an appropiate keyref.

How can this be done? Or is a different approach necessary (integrating the parentid as an additional attribute to the child)?

Thanks in advance,

Erich


--- XML-Instance ---

<?xml version="1.0" encoding="UTF-8"?>
<root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; xsi:noNamespaceSchemaLocation="Multikeys.xsd">
	<parent parentid="1">
		<child childid="4711"/>
		<child childid="4712"/>
		<child childid="4713"/>
	</parent>
	<parent parentid="2">
		<child childid="4711"/>
		<child childid="4715"/>
	</parent>
	<refer>
		<parentRef parentRefId="1">
			<childRef childRefId="4711"/>
		</parentRef>
		<parentRef parentRefId="2">
			<childRef childRefId="4715"/>
		</parentRef>
	</refer>
</root>



--- XML-Schema ---
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"; elementFormDefault="qualified" attributeFormDefault="unqualified">
	<xs:element name="root">
		<xs:complexType>
			<xs:sequence>
				<xs:element name="parent" minOccurs="0" maxOccurs="unbounded">
					<xs:complexType>
						<xs:sequence>
							<xs:element name="child" minOccurs="0" maxOccurs="unbounded">
								<xs:complexType>
									<xs:attribute name="childid" type="xs:int" use="required"/>
								</xs:complexType>
							</xs:element>
						</xs:sequence>
						<xs:attribute name="parentid" type="xs:int" use="required"/>
					</xs:complexType>
					<xs:key name="childKey">
						<xs:selector xpath="./child"/>
						<xs:field xpath="@childid"/>
					</xs:key>
				</xs:element>
				<xs:element name="refer">
					<xs:complexType>
						<xs:sequence>
							<xs:element name="parentRef" maxOccurs="unbounded">
								<xs:complexType>
									<xs:sequence>
										<xs:element name="childRef" maxOccurs="unbounded">
											<xs:complexType>
												<xs:attribute name="childRefId" type="xs:int" use="required"/>
											</xs:complexType>
										</xs:element>
									</xs:sequence>
									<xs:attribute name="parentRefId" type="xs:int" use="required"/>
								</xs:complexType>
							</xs:element>
						</xs:sequence>
					</xs:complexType>
				</xs:element>
			</xs:sequence>
		</xs:complexType>
		<xs:key name="parentKey">
			<xs:selector xpath="./parent"/>
			<xs:field xpath="@parentid"/>
		</xs:key>
	</xs:element>
</xs:schema>

----------------------------------------------
Erich Andresen,                                              ea_6666@freenet.de