[xquery-talk] What does ``UnaryExpr ::= ( <UnaryMinus> | <UnaryPlus> )* ValueExpr'' mean?

[Zhimao Guo]

Dear all,

I am reading XGrammar from W3C released in Oct. 2004.
I am confused by this production rule. What does 
( <UnaryMinus> | <UnaryPlus> )*
mean? Why does the symbol ``*'' occur here?

best regards,
Zhimao Guo