NCBI element colgroup

Abstract	false (This can be used in an instance)
Nillable	false (Instance values cannot use xsi:nil)
Declared Namespaces	xmlns:xsi=http://www.w3.org/2001/XMLSchema-instance xmlns:xlink=http://www.w3.org/1999/xlink xmlns:xs=http://www.w3.org/2001/XMLSchema xmlns:mml=http://www.w3.org/1998/Math/MathML

<xs:element name="colgroup">
    <xs:complexType>
        <xs:sequence>
            <xs:element minOccurs="0" maxOccurs="unbounded" ref="col"/>
        </xs:sequence>
        <xs:attribute name="alternate-form-of" type="xs:IDREF"/>
        <xs:attribute name="content-type"/>
        <xs:attribute name="id" type="xs:ID"/>
        <xs:attribute name="span" default="1"/>
        <xs:attribute name="width"/>
        <xs:attribute name="align">
            <xs:simpleType>
                <xs:restriction base="xs:token">
                    <xs:enumeration value="left"/>
                    <xs:enumeration value="center"/>
                    <xs:enumeration value="right"/>
                    <xs:enumeration value="justify"/>
                    <xs:enumeration value="char"/>
                </xs:restriction>
            </xs:simpleType>
        </xs:attribute>
        <xs:attribute name="char"/>
        <xs:attribute name="charoff"/>
        <xs:attribute name="valign">
            <xs:simpleType>
                <xs:restriction base="xs:token">
                    <xs:enumeration value="top"/>
                    <xs:enumeration value="middle"/>
                    <xs:enumeration value="bottom"/>
                    <xs:enumeration value="baseline"/>
                </xs:restriction>
            </xs:simpleType>
        </xs:attribute>
    </xs:complexType>
</xs:element>

element {}colgroup

Source