Nov. 22—A tense, negotiated hostage exchange and temporary ceasefire between Israel and Hamas is scheduled to go into effect sometime this weekend, possibly as early as Friday morning, local time. It will last only four days, with the possibility of extending it, day-by-day, for a few more days if things proceed as agreed. International aid agencies are already warning that the increased humanitarian aid that is also supposed to flow into Gaza will be far from what is needed and will scarcely ameliorate the human suffering there.