JU wrote:
> Hello,
> I am pretty new in XML and I'm studying the DTD definition. I cannot
> solve a problem, or better, I cannot define what I want in my DTD file.
> What I would like to do is that something like
> <el>text <child/> text</el>
> is accepted but not
> <el>text <child/> text<child/></el>
> 
> I know that <!ELEMENT el (#PCDATA|child)*> declares the element el as a
> mixed content of PCDATA and child but what I want to define is that the
> element child occurs exactly once and not more. Instead of PCDATA can
> occur either before, after or never. I tried with
> (#PCDATA,child+,#PCDATA) but it's not working. Do you know if what I
> want is possible? 

You can't declare that in XML using a DTD (it would be possible in SGML, 
though, but you don't want to go there). If it's essential to use a DTD,
you could use subelements of el, for example

<!ELEMENT el (text,child,text)>
...
<el><text>stuff</text><child/><text>more stuff</text></el>

or use a W3C Schema instead as Martin suggests.

///Peter