Parentheses enclose sequences.
In literal sequence, the item literals are separated by a commas:
(1, 3, 2, 34, 76, -87)
The to operator
generates a range sequence without explicit listing:
(1 to 12)
Using constructors:
(xs:date("2003-03-11"), xs:date("2003-03-12"), xs:date("2003-03-13"), xs:date("2003-03-14"), xs:date("2003-03-15"))
Sequences can have mixed types: (xs:date("2002-03-11"), "Hello", 15)
Sequences do not nest; that is, a sequence cannot be a member of a sequence
Sequences are not sets: they are ordered and can contain duplicates
A single item is the same as a one-element sequence containing the item