Occurence indicator in DTD at the start or for each element?-CodePudding

for a DTD is there a difference between doing this

<!DOCTYPE Book [
 <!ELEMENT Book (Author , a, b, c)>
...
>

and

<!DOCTYPE Book [
 <!ELEMENT Book (Author, a, b, c)
 <!ELEMENT Author (#PCDATA) >
...
>

Is there a difference? If no, Should one be used over the other? Thanks in advance

CodePudding user response：

The most obvious difference is that the first construct is allowed by the XML syntax rules, and the second one isn't. A content model that includes #PCDATA can't include an occurrence indicator.

If it were allowed, it would (logically) mean that one Author element can contain a sequence of text values, which would be indistinguishable from an Author element that contains a single text value. Whereas your first example allows a Book to contain multiple Author elements, which isn't the same thing at all.