It simply means that only the
CvMat
object is allocated and created, but not actual matrix data (not memory for the elements of the matrix themselves), which you can allocate and add later. The instance of this class without actual data still carries
metadata: in this case, just the dimension of the array container and element type descriptor. One purpose of this is to allow the user-allocated data.
Please see:
http://opencv.willowgarage.com/documentation/operations_on_arrays.html[
^].
—SA