Hello, This is a co-occurrance constraint and cannot be enforced in XML Schema. You need a Schematron constraint which restricts the presence of MyElement3 based on the value of the scope attribute: <xsd:element name="MyElement1"> <xsd:annotation> <xsd:appinfo> <pattern xmlns="http://purl.oclc.org/dsdl/schematron" name="Check MyElement3 with scope attr"> <rule context="MyElement1"> <assert test="(MyElement3 and @scope = 'scope2') or not(MyElement3)">MyElement3 is allowed only if @scope is 'scope2'.</assert> </rule> </pattern> </xsd:appinfo> </xsd:annotation> <xsd:complexType> <xsd:sequence> <xsd:element name="Description" minOccurs="0" type="xsd:string"/> <xsd:element maxOccurs="unbounded" ref="MyElement2"/> <xsd:element minOccurs="0" maxOccurs="unbounded" ref="MyElement3"/> <xsd:element maxOccurs="unbounded" ref="MyElement4"/> </xsd:sequence> <xsd:attribute name="scope" use="required"> <xsd:simpleType> <xsd:restriction base="xsd:string"> <xsd:enumeration value="scope1"/> <xsd:enumeration value="scope2"/> <xsd:enumeration value="scope3"/> <xsd:enumeration value="scope4"/> </xsd:restriction> </xsd:simpleType> </xsd:attribute> </xsd:complexType> </xsd:element> In the XML instances you need to specify that the XML Schema contains Schematron constraints, that is insert at the beginning of the XML instance a processing instruction like: <?oxygen SCHSchema="path/to/schemaWithCOConstraint.xsd"?> This processig instruction is inserted automatically if you associate the schema with the XML instance using the Associate Schema action available on the Document toolbar and also on the Document -> XML Document menu. Regards, Sorin Timothy Reaves wrote:

I have an XML Schema I'm trying to lock down (to do more validation for me). I have an element with a required attribute that I restrict as shown below.

<xsd:element name="MyElement1"> <xsd:complexType> <xsd:sequence> <xsd:element name="Description" minOccurs="0" type="xsd:string"/> <xsd:element maxOccurs="unbounded" ref="MyElement2"/> <xsd:element maxOccurs="unbounded" ref="MyElement3"/> <xsd:element maxOccurs="unbounded" ref="MyElement4"/> </xsd:sequence> <xsd:attribute name="scope" use="required"> <xsd:simpleType> <xsd:restriction base="xsd:string"> <xsd:enumeration value="scope1"/> <xsd:enumeration value="scope2"/> <xsd:enumeration value="scope3"/> <xsd:enumeration value="scope4"/> </xsd:restriction> </xsd:simpleType> </xsd:attribute> </xsd:complexType> </xsd:element>

What I want to do is have MyElement3 only allowable in a MyElement1 where scope == scope2 (for example). So have a rule on an element that restricts what element can contain it based on the attribute value.

Is this possible? Any pointer to documentation doing something like this? Thanks!