| <?xml version="1.0" standalone="yes" ?> | |
| <!DOCTYPE document [ | |
| <!ELEMENT document (person*)> | |
| <!ELEMENT person (#PCDATA)> | |
| <!ATTLIST person pnumber ID #REQUIRED> | |
| <!ATTLIST person father IDREF #IMPLIED> | |
| <!ATTLIST person mother IDREF #IMPLIED> | |
| ]> | |
| <document> | |
| <person pnumber="a1">Susan</person> | |
| <person pnumber="a2">Jack</person> | |
| <person pnumber="a3" mother="a1" father="a2">Chelsea</person> | |
| <person pnumber="a4" mother="a1" father="a2">David</person> | |
| </document> |