... as a 30k ... beginner ... supposed to be an attack? ... shimari ...
[Deliberately cutting up your text to create a different meaning.]
A different starting point for your thinking perhaps is 'What is an attack?' on a Go board. Broadly it is a move that threatens to make one of the opponent's groups die later in the game. A form of menacing pressure that if there is no response dire consequences occur. Go has been called the surrounding game, due to this being such an important feature. If a group is first surrounded and second happens to have less than 2 eyes, its removed. While this might seem to be stating the obvious, this continues to be a dominant factor in the game in the dan levels, not just in the double digit kyu levels.
A shimari is a different kind of move. Creating a shimari could be thought of as attacking the empty space on the board, not opponent's groups. Only when the opponent plays a subsequent move near to the shimari does it attack the opponent's stones by restricting the moves that the invading stones can use to make eyes.
Attacking is like putting 2 tanks on either side of your opponent's tank, restricting him that way. A shimari is like using a bulldozer to put an earth mound beside your opponent's tank, restricting his movement in that direction.
Using bulldozers to build fixed fortifications that are not right beside your opponent's tanks perhaps leaves the choice of where to manoeuvre to your opponent. He may not choose to come right up close, because he doesn't feel safe snuggling up to opposing forces. If he isn't up close he isn't being attacked, so you have to rely on your enclosing moves being at least equally efficient as his enclosing moves. A game of ignoring the opponent's moves because you can always spot a bigger plot of empty ground to stake out for yourself. While I don't feel this is best way for a DDK to progress, if you want to do it, look at http://senseis.xmp.net/?Enclosure
and followup into http://senseis.xmp.net/?DoubleWingFormation
. I doubt your opponents will co-operate though.
I feel a better way forward is to try and engage with your opponent, partially attacking him, partially he is attacking you. Dynamic with a lot of difficult judgement about life & death of your stones and his stones. Then work on life & death away from the board and try again. Lots of action and many failures. Hopefully later some successes.
Another good way forward is creating moyos. Look at http://senseis.xmp.net/?Moyo
. It isn't about creating enclosures ( small tight areas where you are pretty sure you can kill anything underneath it, or if it lives get an devastatingly big outside ) but rather billowing frameworks where you wish the opponent comes in so you can attack him and consolidate half the original framework as solid territory. No partially he attacks you while you attack him. No fair fight. A nice big black dark back alley where he has an unfair fight on your turf with one hand tied behind his back.
In your example
is not an attack. It doesn't restrict or threaten the life of any of the black stones. The
stone is immediately restricted by the 2 nearest black stones that form a shimari close to the corner. It isn't under attack as it has two directions towards the centre where extra connecting moves can be made, so it will live. Its virtue is it prevents the whole of that quarter of the board becoming black territory. It probably won't create white territory, but it reduces the amount that black can get.
is an attack because it restricts one of the two directions for white's connect away moves to the centre. It also blocks moves into the side. If there was no response to
, a further black move in the centre would have a very surrounding feel, threatening to cause