Is it possible to have multiple substitutiongroups per element type?

Question

Say you have the following in a schema:

    <xsd:complexType name="shape"/>

    <xsd:complexType name="circle">
            <xsd:complexContent>
                <xsd:extension base="shape">
                    <xsd:attribute name="radius" type="xsd:double"/>
                </xsd:extension>
            </xsd:complexContent>
    </xsd:complexType>

    <xsd:complexType name="arc">
                <xsd:complexContent>
                    <xsd:extension base="circle">
                        <xsd:attribute name="startAngle" type="xsd:double"/>
                        <xsd:attribute name="endAngle" type="xsd:double"/>
                    </xsd:extension>
                </xsd:complexContent>
    </xsd:complexType>

It is then possible to add a substitution group like this

<xsd:element name="shape" type="shape" abstract="true"/>
<xsd:element name="circle" type="circle" substitutionGroup="shape"/>
<xsd:element name="arc" type="arc" substitutionGroup="shape"/>

and then take in any of those types by referencing the group like:

<xsd:element ref="shape"/>

That part isn't a problem.

But what if I also want to be able to allow (in another section) just circle and its subtype?

Is it possible to add multiple substitutiongroups in order to emulate proper inheritance in a schema? I tried adding another element type like:

<xsd:element name="shape" type="shape" abstract="true"/>
<xsd:element name="circle" type="circle" substitutionGroup="shape"/>
<xsd:element name="arc" type="arc" substitutionGroup="shape"/>
<xsd:element name="arc2" type="arc" substitutionGroup="circle"/>

But I'd rather not have to change the name of the expected element depending on what I'm expecting.

Is there a better way to do this?

Answer 1

You should be able to just keep arc as a substitute for circle. Wherever you use shape, either circle or arc then apply, and where you use circle, either circle or arc.