RE: Unqualified forms and Inheritance by Restriction

This seems to argue that the tools that “accept” what I am doing now, do so in error. Which I had an uneasy feeling they did.

>>Because the element declaration isn't global, the only way you can replace it with a different element declaration of the same name is by putting that declaration in a schema >>document whose target namespace is {Base}.

The issue here is that if element {Base}E1 is mandatory in the base type, it's not good enough to have an element {Restricted}E1 in its place in the derived type: the elements must have the same name.

Because the element declaration isn't global, the only way you can replace it with a different element declaration of the same name is by putting that declaration in a schema document whose target namespace is {Base}.

XSD 1.1 solves this by allowing you to specify targetNamespace as an attribute on a local element declaration. In 1.0, though, there's no alternative to putting the restricted type in a schema document for the {Base} namespace -- even if this means tresspassing on someone else's namespace.

Michael Kay
Saxonica

On 16/03/2012 13:47, Toby Considine wrote:

I have a family of schemas for energy markets that are derived from a root abstract schema. In most cases, the derived types extend the abstract types by adding additional elements. This inheritance by addition is straight-forward.

For one key abstract type, I use inheritance by restriction. Derived types must have all the elements of the root type, but they may be restricted to a few enumerated values. Consider the following, simplified and stripped down:

Root Schema:

<xs:schema xmlns:xs=http://www.w3.org/2001/XMLSchema xmlns=http://www.example.org/Base targetNamespace=http://www.example.org/Base elementFormDefault="qualified">

<xs:element name="A" type="AType"/>

<xs:complexType name="AType" abstract="true">

                <xs:sequence>

                                <xs:element name="E1" type="xs:string"/>

                                <xs:element name="E2" type="xs:string" />

                </xs:sequence>

</xs:complexType>

Derivative schema

<xs:schema xmlns:xs=http://www.w3.org/2001/XMLSchema xmlns=http://www.example.org/Restriction xmlns:base=http://www.example.org/Base targetNamespace=http://www.example.org/Restriction elementFormDefault="qualified">

<xs:import namespace=http://www.example.org/Base schemaLocation="Base.xsd"/>

<xs:element name="ARestricted" type="ARestrictedType"/>

<xs:complexType name="ARestrictedType" abstract="false">

<xs:complexContent>

                <xs:restriction base="base:AType">

                                <xs:sequence>

                                                <xs:element name="E1"  type="xs:string" fixed="foo"/>

                                                <xs:element name="E2">

                                                                <xs:simpleType>

                                                                                <xs:restriction base="xs:token">

                                                                                                <xs:enumeration value="fie"/>

                                                                                                <xs:enumeration value="foe"/>

                                                                                </xs:restriction>

                                                                </xs:simpleType>

                                                </xs:element>

                                </xs:sequence>

                </xs:restriction>

</xs:complexContent>

</xs:complexType>

The derivative schema is invalid. In particular, when processed, each element in ARestricted generates the following error:  "rcase-NameAndTypeOK.1: The declarations' {name}s and {target namespace}s are not the same: restriction element is <xs:element name="itemDescription"> and base element is <xs:element name="itemDescription">."

http://www.w3.org/TR/2004/REC-xmlschema-1-20041028/#rcase-NameAndTypeOK

I can avoid the error if I change each of the schemas from elementFormDefault="qualified" to elementFormDefault="unqualified". The derived schema now validates using XML Spy and Liquid XML Studio. When I use the Liquid Technologies code generation tool to create software objects, the objects generate XML that looks like what I want.

Here’s the question:

Should I be looking for some side effect of switching these schemas from qualified to unqualified? Is there some hidden problem I will come upon if I require conforming schemas to be unqualified? I generally prefer “qualified” for the esthetic reason that I like to see explicit type derivations (prefices) in the schema. I do not have a feel for what else may be affected.

Thanks

tc