The form in which the starting term is specified is given by parameter
The syntax this parameter is similar to the RPN query as described in
yaz_search(). It consists of zero or more
@attr-operator specifications, then followed by
exactly one token.
This optional parameter specifies additional information to control
the behaviour of the scan request. Three indexes are currently read
from the flags array:
number (number of terms requested),
position (preferred position of term) and
stepSize (preferred step size).