ELEMENT – a valid tag
ATTLIST – attributes within a tag
PCDATA – parsed character data
CDATA – (literal) character data
ENTITY – user defined text
no postfix – exactly 1 occurence
* – 0,1,n occurences
+ – 1,n occurences
? – 0,1 occurences
, – one element followed by the other in the specified order
| – one element or the other
Links:
XML 1.0 – W3
XML Guide – Wattle
DTD Tutorial – W3Schools
DTD Tutorial – zvon
Reading a DTD
Creating DTDs – Devguy
XML Primer – Swint
DTD – Wikipedia
DTD – XMLFiles