def sentence_position(i, size):
    """Different sentence positions indicate different
    probability of being an important sentence.
    """
    normalized = i * 1.0 / size
    if normalized > 1.0:
        return 0
    elif normalized > 0.9:
        return 0.15
    elif normalized > 0.8:
        return 0.04
    elif normalized > 0.7:
        return 0.04
    elif normalized > 0.6:
        return 0.06
    elif normalized > 0.5:
        return 0.04
    elif normalized > 0.4:
        return 0.05
    elif normalized > 0.3:
        return 0.08
    elif normalized > 0.2:
        return 0.14
    elif normalized > 0.1:
        return 0.23
    elif normalized > 0:
        return 0.17
    else:
        return 0
