<xsd:element name="bond" id="el.bond">
    <xsd:annotation>
        <xsd:documentation>
            <h:div class="summary" xmlns:h="http://www.w3.org/1999/xhtml">A bond between atoms, or between atoms and bonds.</h:div>
            <h:div class="description" xmlns:h="http://www.w3.org/1999/xhtml">_bond_ is a child of _bondArray_ and contains bond information. Bond must refer to at least two atoms (normally using _atomRefs2_) but may also refer to more for multicentre bonds. Bond is often EMPTY but may contain _electron_, _length_ or _bondStereo_ elements.</h:div>
            <h:div class="example" href="bond1.xml" xmlns:h="http://www.w3.org/1999/xhtml" />
            <!--            
            <h:div class="example" href="bond2.xml"></h:div>
-->
        </xsd:documentation>
        <xsd:documentation>
            <h:div class="validation" href="cmlCore.val.bond.xml" xmlns:h="http://www.w3.org/1999/xhtml" />
        </xsd:documentation>
        <xsd:appinfo>
            <comment xmlns="">Validate Bonds</comment>
            <template match="bond" id="val-bond" xmlns="">
                <comment>Atom Refs for 2-atom bond</comment>
                <variable name="at1" select="substring-before(normalize-space(@atomRefs2),' ')" />
                <variable name="at2" select="substring-after(normalize-space(@atomRefs2),' ')" />
                <comment>Are atoms distinct?</comment>
                <if test="$at1 = $at2">
                    <call-template name="error">
                        <with-param name="error">BOND (<value-of select="@id" />): ATOMS not distinct: <value-of select="$at1" /></with-param>
                    </call-template>
                </if>
                <comment>Do both atoms exist in current molecule context?</comment>
                <if test="not(key('atoms', $at1))">
                    <call-template name="error">
                        <with-param name="error">BOND (<value-of select="@id" />): ATOMREF not found: <value-of select="$at1" /></with-param>
                    </call-template>
                </if>
                <if test="not(key('atoms', $at2))">
                    <call-template name="error">
                        <with-param name="error">BOND (<value-of select="@id" />): ATOMREF not found: <value-of select="$at2" /></with-param>
                    </call-template>
                </if>
            </template>
        </xsd:appinfo>
    </xsd:annotation>
    <xsd:complexType id="bond.content.id">
        <xsd:choice>
            <xsd:choice minOccurs="0" maxOccurs="unbounded">
                <xsd:element ref="bondType" />
                <xsd:element ref="electron">
                    <xsd:annotation>
                        <xsd:documentation>
                            <h:div class="summary" xmlns:h="http://www.w3.org/1999/xhtml">One or more electrons associated with the bond.</h:div>
                            <h:div class="description" xmlns:h="http://www.w3.org/1999/xhtml">The _bondRef_ on the _electron_ should point to the id on the bond. We may relax this later and allow reference by context.</h:div>
                        </xsd:documentation>
                    </xsd:annotation>
                </xsd:element>
                <xsd:element ref="bondStereo">
                    <xsd:annotation>
                        <xsd:documentation>
                            <h:div class="summary" xmlns:h="http://www.w3.org/1999/xhtml">The stereo convention for the bond.</h:div>
                            <h:div class="general" xmlns:h="http://www.w3.org/1999/xhtml">only one convention allowed.</h:div>
                        </xsd:documentation>
                    </xsd:annotation>
                </xsd:element>
            </xsd:choice>
        </xsd:choice>
        <xsd:attributeGroup ref="title" />
        <xsd:attributeGroup ref="id" />
        <xsd:attributeGroup ref="convention" />
        <xsd:attributeGroup ref="dictRef" />
        <xsd:attributeGroup ref="ref" />
        <xsd:attributeGroup ref="atomRefs2" />
        <xsd:attributeGroup ref="atomRefs">
            <xsd:annotation>
                <xsd:documentation>
                    <h:div class="specific" xmlns:h="http://www.w3.org/1999/xhtml">This is designed for multicentre bonds (as in delocalised systems or electron-deficient centres. The semantics are experimental at this stage. As an example, a B-H-B bond might be described as
                 &lt;bond atomRefs="b1 h2 b2"/.</h:div>
                </xsd:documentation>
            </xsd:annotation>
        </xsd:attributeGroup>
        <xsd:attributeGroup ref="bondRefs">
            <xsd:annotation>
                <xsd:documentation>
                    <h:div class="specific" xmlns:h="http://www.w3.org/1999/xhtml">This is designed for pi-bonds and other systems where formal valence bonds are not drawn to atoms. The semantics are experimental at this stage. As an example, a Pt-|| bond (as the Pt-ethene bond in Zeise's salt) might be described as &lt;bond atomRefs="pt1" bondRefs="b32"/.</h:div>
                </xsd:documentation>
            </xsd:annotation>
        </xsd:attributeGroup>
        <xsd:attributeGroup ref="order" />
    </xsd:complexType>
</xsd:element>