DOCBOOK: schema

Anyone have information on where I can find a full list of all the symbols
in the element content model that tells what's required or allowed?

For example ... things like the +, how to say only one, exclusive or's,
etc...

Sect1 ::=
(Sect1Info?,
 (Title,Subtitle?,TitleAbbrev?),
  ^^^^^
 (ToC|LoT|Index|Glossary|Bibliography)*,
 (((CalloutList|GlossList|ItemizedList|OrderedList|SegmentedList|
    SimpleList|VariableList|Caution|Important|Note|Tip|Warning|
    ...


Thanks,