As already seen you can declare namespaces with the namespace directive. When declared it places a symbol inside the scope the parent namespace so the labels inside can be accessed as local fields of the namespace symbol:
.namespace vic { .label borderColor = $d020 .label backgroundColor0 = $d021 .label backgroundColor1 = $d022 .label backgroundColor2 = $d023 } lda #0 sta vic.backgroundColor0 sta vic.borderColor
Namespaces are normally used to make sure that code in a source file (Like a library) is not colliding with other parts of the code. For this, Place the filenamespace directive at the top of the file and everything after that is placed in the desired namespace:
/* FILE 0 */ jsr part1.init jsr part1.exec jsr part2.init jsr part2.exec rts
/* FILE 1 */ .filenamespace part1 init: ... rts exec: ... rts
/* FILE 2 */ .filenamespace part2 init: ... rts exec: ... rts