谁帮注释下这个简单程序
<!ELEMENT addresses:address (addresses:buildingnumber, addresses:street,addresses:city, addresses:state, addresses:zip)>
<!ATTLIST addresses:address xmlns:addresses CDATA #IMPLIED>
<!ELEMENT addresses:buildingnumber (#PCDATA)>
<!ELEMENT addresses:street (#PCDATA)>
<!ELEMENT addresses:city (#PCDATA)>
<!ELEMENT addresses:state (#PCDATA)>
<!ELEMENT addresses:zip (#PCDATA)>
//不胜感激
