This is an XSD Schema generated from the Relax NG Schema described in Section 3.1.
<schema
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:om="http://www.openmath.org/OpenMath" elementFormDefault="qualified" targetNamespace="http://www.openmath.org/OpenMath">
<!-- OpenMath object constructor -->
<element name="OMOBJ">
<complexType>
<group ref="om:omel"/>
<attributeGroup ref="om:compound.attributes"/>
<attribute name="version" type="xs:string"/>
</complexType>
</element>
<!-- Elements which can appear inside an OpenMath object -->
<group name="omel">
<choice>
<element ref="om:OMS"/>
<element ref="om:OMV"/>
<element ref="om:OMI"/>
<element ref="om:OMB"/>
<element ref="om:OMSTR"/>
<element ref="om:OMF"/>
<element ref="om:OMA"/>
<element ref="om:OMBIND"/>
<element ref="om:OME"/>
<group ref="om:OMATTR"/>
<element ref="om:OMR"/>
</choice>
</group>
<!-- things which can be variables -->
<group name="omvar">
<choice>
<element ref="om:OMV"/>
<group ref="om:attvar"/>
</choice>
</group>
<group name="attvar">
<sequence>
<element name="OMATTR">
<complexType>
<sequence>
<element ref="om:OMATP"/>
<choice>
<element ref="om:OMV"/>
<group ref="om:attvar"/>
</choice>
</sequence>
<attributeGroup ref="om:common.attributes"/>
</complexType>
</element>
</sequence>
</group>
<attributeGroup name="cdbase">
<attribute name="cdbase" type="xs:anyURI"/>
</attributeGroup>
<!-- attributes common to all elements -->
<attributeGroup name="common.attributes">
<attribute name="id" type="xs:ID"/>
</attributeGroup>
<!-- attributes common to all elements that construct compount OM objects. -->
<attributeGroup name="compound.attributes">
<attributeGroup ref="om:common.attributes"/>
<attributeGroup ref="om:cdbase"/>
</attributeGroup>
<!-- symbol -->
<element name="OMS">
<complexType>
<attributeGroup ref="om:common.attributes"/>
<attribute name="name" use="required" type="xs:NCName"/>
<attribute name="cd" use="required" type="xs:NCName"/>
<attributeGroup ref="om:cdbase"/>
</complexType>
</element>
<!-- variable -->
<element name="OMV">
<complexType>
<attributeGroup ref="om:common.attributes"/>
<attribute name="name" use="required" type="xs:NCName"/>
</complexType>
</element>
<!-- integer -->
<element name="OMI">
<complexType>
<simpleContent>
<restriction base="xs:anyType">
<simpleType>
<restriction base="xs:string">
<pattern value="\s*(-\s?)?[0-9]+(\s[0-9]+)*\s*"/>
</restriction>
</simpleType>
<attributeGroup ref="om:common.attributes"/>
</restriction>
</simpleContent>
</complexType>
</element>
<!-- byte array -->
<element name="OMB">
<complexType>
<simpleContent>
<extension base="xs:base64Binary">
<attributeGroup ref="om:common.attributes"/>
</extension>
</simpleContent>
</complexType>
</element>
<!-- string -->
<element name="OMSTR">
<complexType mixed="true">
<attributeGroup ref="om:common.attributes"/>
</complexType>
</element>
<!-- IEEE floating point number -->
<element name="OMF">
<complexType>
<attributeGroup ref="om:common.attributes"/>
<attribute name="dec" type="xs:double"/>
<attribute name="hex">
<simpleType>
<restriction base="xs:string">
<pattern value="[0-9A-F]+"/>
</restriction>
</simpleType>
</attribute>
</complexType>
</element>
<!-- apply constructor -->
<element name="OMA">
<complexType>
<group maxOccurs="unbounded" ref="om:omel"/>
<attributeGroup ref="om:compound.attributes"/>
</complexType>
</element>
<!-- binding constructor -->
<element name="OMBIND">
<complexType>
<sequence>
<group ref="om:omel"/>
<element ref="om:OMBVAR"/>
<group ref="om:omel"/>
</sequence>
<attributeGroup ref="om:compound.attributes"/>
</complexType>
</element>
<!-- variables used in binding constructor -->
<element name="OMBVAR">
<complexType>
<group maxOccurs="unbounded" ref="om:omvar"/>
<attributeGroup ref="om:common.attributes"/>
</complexType>
</element>
<!-- error constructor -->
<element name="OME">
<complexType>
<sequence>
<element ref="om:OMS"/>
<choice minOccurs="0" maxOccurs="unbounded">
<group ref="om:omel"/>
<element ref="om:OMFOREIGN"/>
</choice>
</sequence>
<attributeGroup ref="om:common.attributes"/>
</complexType>
</element>
<!-- attribution constructor and attribute pair constructor -->
<group name="OMATTR">
<sequence>
<element name="OMATTR">
<complexType>
<sequence>
<element ref="om:OMATP"/>
<group ref="om:omel"/>
</sequence>
<attributeGroup ref="om:compound.attributes"/>
</complexType>
</element>
</sequence>
</group>
<element name="OMATP">
<complexType>
<sequence maxOccurs="unbounded">
<element ref="om:OMS"/>
<choice>
<group ref="om:omel"/>
<element ref="om:OMFOREIGN"/>
</choice>
</sequence>
<attributeGroup ref="om:compound.attributes"/>
</complexType>
</element>
<!-- foreign constructor -->
<element name="OMFOREIGN">
<complexType mixed="true">
<choice minOccurs="0" maxOccurs="unbounded">
<group ref="om:omel"/>
<group ref="om:notom"/>
</choice>
<attributeGroup ref="om:compound.attributes"/>
<attribute name="encoding" type="xs:string"/>
</complexType>
</element>
<!--
Any elements not in the om namespace
(valid om is allowed as a descendant)
-->
<group name="notom">
<sequence>
<choice minOccurs="0">
<any namespace="##other" processContents="skip"/>
<any namespace="##local" processContents="skip"/>
</choice>
</sequence>
</group>
<!-- reference constructor -->
<element name="OMR">
<complexType>
<attributeGroup ref="om:common.attributes"/>
<attribute name="href" use="required" type="xs:anyURI"/>
</complexType>
</element>
</schema>