why is "ComputedConstructor" not in any right hand side in the core grammar?

Hello,

Could anybody tell me:

why are OrderByClause, QuantifiedExpr and ComputedConstructor
not in any right hand side of any production in the core grammar?

http://www.w3.org/TR/xquery-semantics/#sec_core
A.1 Core BNF
[39 (Core)]    OrderByClause
[43 (Core)]    QuantifiedExpr
[57 (Core)]    ComputedConstructor


Thanks.

Xiaobo Peng