The group of Information Security Marking attributes in which the use of attributes
'classification' and 'ownerProducer' is optional.
This group is to be contrasted with group 'SecurityAttributesGroup' in which use of
these attributes is required.
This attribute is only a placeholder so that all the ISM attributes are not shown
in the schemaGuide for every element. If you refer to the documentation of the
attribute group it will say what attributes should be here.
Source
<xsd:attributeGroup name="SecurityAttributesOptionGroup"><xsd:annotation><xsd:documentation xml:lang="en">The group of Information Security Marking attributes in which the use of attributes 'classification' and 'ownerProducer' is optional. This group is to be contrasted with group 'SecurityAttributesGroup' in which use of these attributes is required.</xsd:documentation></xsd:annotation><xsd:attribute ref="SchemaguideSecurityAttributesOptionGroup" use="optional"/></xsd:attributeGroup>