One of the key protocols for referees is to follow is the dictum of only ruling on what is clear and obvious on the pitch.
For your average, every day game of footy, without the benefit of assistant referees with radio communication to the main referee, this means if you can't clearly observe an infringement on the field then play continues.
There may be a few moans and groans from players who think they have seen an infringement, but they normally get over it pretty quickly and get on with the game.
For the referee, guessing is fraught with danger and is to be avoided at all costs.
But for games such as the quarterfinals in Japan last weekend, there are Television Match Officials (the TMO) who have all the technology to ensure the correct decisions are made by referees.
So "clear and obvious" with the aid of a TMO should ensure absolute precision in refereeing decision making. Or does it?
Looking at the All Blacks match against Ireland, the first incident of note was the deliberate knock-on by the Irish winger Jacob Stockdale, which was a clear and obvious as the ball was knocked downwards, meaning there was no chance of him regathering.
I have seen yellow cards issued for the same infringement from a similar place on the field, but it did cost the Irish three points anyway.
Replays show the Kieran Read tackle without the ball shortly after halftime was clear and obvious, as was the shoulder charge into the ruck by the Irish flanker Peter O'Mahony, so the TMO earned his money on this occasion.
There were a few instances where the referee and TMO seemed to come to decisions that for me were not so clear and obvious.
The Irish prop Tadhg Furlong was ruled to have knocked the ball on after receiving an unexpected tap down from a lineout.
The ball did go forward, but he was facing his goal line and the ball seemed to have actually travelled backwards rather than forwards towards the All Blacks' line.
Fellow prop Cian Healy was penalised for picking up a loose ball up at a ruck and heading towards the try line, presumably for being offside.
Without the benefit of endless replays, he didn't look offside to me, but it can be a fine line for this particular offence.
The decision which surprised me the most though, was the yellow card handed to Matt Todd for being "clearly offside" at a ruck on the goal line.
The line is part of the in-goal area, so as long as his feet were on the line then he would be onside.
To rub salt into the wound, Todd ended up being knocked over against the goal post, thus preventing the grounding of the ball against it to score a try, which the Irishman with the ball was trying to do.
This decision cost the All Blacks a penalty try as well as the loss of a player, so it could have been a critical one had the scores been very close at that late stage.
However, Sonny Bill Williams was clearly offside at the same phase of play, so just a penalty seemed a more obvious outcome of the incident.
There were a few things the referee and the TMO missed though.
Aaron Smith's first try came after Brodie Retallick had illegally cleaned out an Irishman clearly from the side rather than directly from behind the ruck leading up to the try.
Todd scored his try with the aid of another illegal clean out from the side, this time by Beauden Barrett.
In attempting to prevent a kick from going into touch after it had crossed the touch line, George Bridge seemed to have one foot on the ground at the time he threw the ball back into the field of play.
I don't think there is any doubt that the red card handed out to Frenchman Sébastien Vahaamahina in the Welsh game was deserved.
This is what the red card should be used for – deliberate acts of clear foul play, particularly to the head of an opponent.
Yellow-card decisions are often not so clear cut.
In particular, cards handed out for some of the high tackles during the tournament seem to show there is an inconsistency in this area.
In this respect, World Rugby seems to have chucked the referees under the bus to a certain extent with their directive to clamp down on this offence after the first few games.
A few other observations.
The Irish were in no hurry to set their lineout, and then wasted more time while the front player came and delivered instructions to the thrower.
No doubt the speed of the game was getting to them, but referees have the power to stop this sort of time wasting.
In that respect, Nigel Owens was right to stop them throwing the ball around before a drop out on one occasion.
Goal line defenders diving at the feet of attackers instead of trying to tackle opponents when their goal line is under siege should be penalised.
This is a common ploy but really comes under the guise of dangerous play.
Having said all that, the play of the All Blacks last weekend was breath-takingly stunning.
The accuracy of the passing and the defensive organisation was clear and obvious for all to see.
I hope they can repeat it again tonight.