<!ELEMENT company (name, ticker_symbol?, description?,
          business_code, partners?, competitors?)>
<!ELEMENT name (#PCDATA)>
<!ELEMENT ticker_symbol (#PCDATA)>
<!ELEMENT description (#PCDATA)>
<!ELEMENT business_code (#PCDATA)>
<!ELEMENT partners (partner+)>
<!ELEMENT partner (#PCDATA)>
<!ELEMENT competitors (competitor+)>
<!ELEMENT competitor (#PCDATA)>