Left- and double-coset decompositions of space groups
are systematically analysed by putting the emphasis on
the introduction of special auxiliary groups. An
algorithm is tailored to exploit the specific structure of
space groups. The new results are, amongst others, an
efficient alternative method to determine for space
groups minimal sets of double-coset representatives and
a general formula that gives the structure and number of
left cosets that are contained in double cosets. Left-coset
and double-coset decompositions of space groups are
exploited in domain structure analysis.