<[
        <!ELEMENT Message (AvailabilityWeb)*>
        <!ATTLIST Message
                source CDATA #REQUIRED
                target CDATA #REQUIRED
                type CDATA #REQUIRED>
        <!ELEMENT AvailabilityWeb (#PCDATA)>
        <!ATTLIST AvailabilityWeb
                company CDATA #REQUIRED
                sum_availability CDATA #REQUIRED
                offer CDATA #REQUIRED>
        ]>