
        To allow for a clear a simple definition of all span relations (overlapping and ordering between spans),
        we see a span as the interval of real numbers that include the start offset and everything else that is
        larger than the start offset but smaller than the end offset. This means for a zero length span
        Span(x,x), the number x is contained in the span, but no other number &gt; x.

        Two spans overlap, if there is at least one integer that is included in both number set