dtd_state

<!ELEMENT world (continent+)>

<!ELEMENT continent (state+)>
<!ATTLIST continent name CDATA #REQUIRED>

<!ELEMENT state (industry)>
<!ATTLIST state name CDATA #REQUIRED>
<!ATTLIST state capital CDATA "none">
<!ATTLIST state area CDATA "0">
<!ATTLIST state population CDATA "0">

<!ELEMENT industry (heavy?,light?)>

<!ELEMENT heavy (automotive?,mining?,chemical?,energy?,metallurgy?,aviation?,building?,mechanical?)>

<!ELEMENT automotive (#PCDATA)>
<!ELEMENT mining (#PCDATA)>
<!ELEMENT chemical (#PCDATA)>
<!ELEMENT energy (#PCDATA)>
<!ELEMENT metallurgy (#PCDATA)>
<!ELEMENT aviation (#PCDATA)>
<!ELEMENT building (#PCDATA)>
<!ELEMENT mechanical (#PCDATA)>

<!ELEMENT light (electrical?,printing?,foodstuff?,textile?)>

<!ELEMENT electrical (#PCDATA)>
<!ELEMENT printing (#PCDATA)>
<!ELEMENT foodstuff (#PCDATA)>
<!ELEMENT textile (#PCDATA)>