Here is the DTD specified by the USPTO:
<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE us-patent-assignments [<!ELEMENT us-patent-assignments (action-key-code, transaction-date, patent-assignments)> <!ATTLIST us-patent-assignments dtd-version CDATA #IMPLIED date-produced CDATA #IMPLIED> <!ELEMENT action-key-code (#PCDATA)>
<!ELEMENT transaction-date (date)>
<!ELEMENT patent-assignments (data-available-code | patent-assignment+)> <!ELEMENT date (#PCDATA)> <!ELEMENT data-available-code (#PCDATA)> <!ELEMENT patent-assignment (assignment-record, patent-assignors, patent-assignees, patent-properties)> <!ELEMENT assignment-record (reel-no, frame-no, last-update-date, purge-indicator, recorded-date, page-count?, correspondent, conveyance-text)> <!ELEMENT patent-assignors (patent-assignor+)> <!ELEMENT patent-assignees (patent-assignee+)> <!ELEMENT patent-properties (patent-property+)> <!ELEMENT reel-no (#PCDATA)> <!ELEMENT frame-no (#PCDATA)> <!ELEMENT last-update-date (date)> <!ELEMENT purge-indicator (#PCDATA)> <!ELEMENT recorded-date (date)>
<!ELEMENT page-count (#PCDATA)>
<!ELEMENT correspondent (name, address-1?, address-2?, address-3?, address-4?)>