Life In 19x19

I am reviewing this joseki (which doesn't appear much according to my database), but I'm having trouble understanding the purpose behind W2-4. Is it just to leave some aji? To make it easier to keep black blocked in at 'a' (though I'm not sure why that is better than just playing at 'a' directly)? Sometimes moves like this are to help white get a good position by squeezing black in, but I don't see how that is doing this here. I appreciate any insight.

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[go]$$ Joseki Question
$$-------------------------------+
$$ . . . . . . . . 3 5 4 . . . . |
$$ . . . . . . a X O X 2 . . . . |
$$ . . . . . . O O X X O . . . . |
$$ . . . . . , . . O O 1 , X . . |
$$ . . . . . . . . . . . X . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |[/go]

I think I saw this somewhere in a book. The moves are made because afterwards, white can wall black in like this (not sure about 5 though):

Click Here To Show Diagram Code

[go]$$W Joseki Question
$$-------------------------------+
$$ . . . . . . 3 . X X O . . . . |
$$ . . . . . . 1 X . X O 4 . . . |
$$ . . . . . . O O X X O 2 . . . |
$$ . . . . . , . . O O X , X . . |
$$ . . . . . 5 . . . . . X . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |[/go]

Maybe you can also post the beginning of the joseki? (I would be curious how this position arises - cannnot find it in one of my books.)

Click Here To Show Diagram Code

[go]$$B Joseki Question
$$-------------------------------+
$$ . . . . . . 8 0 3 5 4 . . . . |
$$ . . . . . . 6 X O X 2 9 . . . |
$$ . . . . . . O O X X O 7 . . . |
$$ . . . . . , . . O O 1 , X . . |
$$ . . . . . . . . . . . X . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |[/go]

Click Here To Show Diagram Code

[go]$$ Joseki Question
$$-------------------------------+
$$ . . . . . . 4 5 3 . . . . . . |
$$ . . . . . . 2 X O X 6 . . . . |
$$ . . . . . . O O X X O 7 . . . |
$$ . . . . . , . . O O 1 , X . . |
$$ . . . . . . . . . . . X . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |[/go]

The situation appears similar, except the first situation white has one more point (and a half point ko...)

Obviously 8 onwards is endgame in the first diagram, and the 6/7 exchange wouldn't be played in the second diagram. Also if in the second diagram 4 at 6, 5 at 7 (and the 4 5 exchange later)

Free point ?

Bonus Material for Beginners

I think it is also good because it leaves more ko threats.

The sacrifice gains points (count it) and also allows an atari against . This atari alone is worth a lot in terms of outside influence.

Click Here To Show Diagram Code

[go]$$ Joseki Question
$$-------------------------------+
$$ . . . . . b a . X X O . . . . |
$$ . . . . . . 4 X . X O . . . . |
$$ . . . . . . O O X X O 5 . . . |
$$ . . . . . , . . O O X 3 X . . |
$$ . . . . . . . . . . 2 X . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |[/go]

True, white gets the atari at 2, which is worth something; but white could get that without putting the two extra stones inside. I think the real value is that white 4 is sente, and then either a or b is also sente, which may help if fighting breaks out to the left of this position. I think white should hold this in reserve, until certain which one (a or b) he wants to play.

On a related note, I have always preferred black in this joseki. Black gets a lot of points. White has some "influence", but it still has a lot of cutting points.

Yeah, I'd rather have the influence than not, but it doesn't seem worth all of the points that black racks up.

Am I the only one that feels this way?

I didn't even know the joseki. FWIW, I think White can have a happy result if his position in the top left is good enough. That's the story of pretty much every joseki though

Thanks all for the helpful insight.

As noted, this is not a common joseki (at least not in the past few decades), but surely it can be appropriate depending on the whole board position (the same can be said for nearly every sequence).

I'm studying such joseki not because I want to try them out per se, but to get a feel for efficient shape and work on positional judgment. If a sequence was considered joseki even 70 years ago, I think it is still helpful (for me) to study it for this purpose. In the current example, for instance, the two moves are still good moves if you find yourself in this position; now I sort-of know why .

I think it`s worth noticing (forgive me for sounding like a broken record if you were in KGS chat with me this afternoon ...)

That the joseki is (generally speaking) always left at-

Click Here To Show Diagram Code

[go]$$W Joseki Question
$$-------------------------------+
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . 3 . a . 1 . . . . |
$$ . . . . . , . . . . . , X . . |
$$ . . . . . . . . . . b 2 . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |[/go]

And is generally not revisited until very late in the fuseki - when both players have much more information to work with. Also probably worth noticing (as Shaddy pointed out to me) that the black a white b exchange appears much more common (continuation varies depending on surroundings...).

judicata wrote:I am reviewing this joseki (which doesn't appear much according to my database), but I'm having trouble understanding the purpose behind W2-4. Is it just to leave some aji? To make it easier to keep black blocked in at 'a' (though I'm not sure why that is better than just playing at 'a' directly)? Sometimes moves like this are to help white get a good position by squeezing black in, but I don't see how that is doing this here. I appreciate any insight.

$$ Joseki Question
$$-------------------------------+
$$ . . . . . . . . 3 5 4 . . . . |
$$ . . . . . . a X O X 2 . . . . |
$$ . . . . . . O O X X O . . . . |
$$ . . . . . , . . O O 1 , X . . |
$$ . . . . . . . . . . . X . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |

Click Here To Show Diagram Code

[go]$$ Joseki Question
$$-------------------------------+
$$ . . . . . . . . 3 5 4 . . . . |
$$ . . . . . . a X O X 2 . . . . |
$$ . . . . . . O O X X O . . . . |
$$ . . . . . , . . O O 1 , X . . |
$$ . . . . . . . . . . . X . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . . . |[/go]

One of the reasons for the joseki moves is that Black will eventually have to remove the three white stones from the board (semedori) so actuall White loses nothing by playing these moves and seals Black in from the outside and to the left. Furthermore, if Black plays at a in the diagram his stones will be alive and he won't have to take off the three white stones.