<!ELEMENT pingus-world (name,description-list,background,level-list)>
<!ELEMENT name (#PCDATA)>
<!ATTLIST name          
        xml:lang CDATA #REQUIRED>
<!ELEMENT description-list (description*)>

<!ELEMENT description (#PCDATA)>
<!ATTLIST description          
        xml:lang CDATA #REQUIRED>

<!ELEMENT background (surface)>
<!ELEMENT surface (resource)>

<!ELEMENT resource (resource-file, resource-ident)>
<!ELEMENT resource-file (#PCDATA)>
<!ELEMENT resource-ident (#PCDATA)>

<!ELEMENT level-list (level*)>
<!ELEMENT level (#PCDATA)>