From An Introduction to XML Basic Information Track Computational Science Course CPS616 -- Spring Semester 1999. byNancy McCracken,Ozgur Balsoy, Tom Scavo
Quantity indicators can also be used.
`?' indicates an element is optional or cannot repeat
`+' indicates an element is required and may repeat
`*' indicates an element is optional, and also repeatable
Document text is indicated by the keyword PCDATA (Parsable Character Data) <!ELEMENT emph (#PCDATA|sub|super)*> <!ELEMENT sub (#PCDATA)> <!ELEMENT super (#PCDATA)> <emph>H<subɮ</subɬ is water.</emph>