Classification of positions
A: By phases of the game
Here there are opening, middle game and endgame positions, and it is probably useful to subdivide each into early/late:
- early opening positions are mostly about occupation of corners and playing approaches and enclosures, until joseki start;
- late opening positions involve occupation of big points and the decision about who will invade first;
- early middle game positions feature invasions and running fights;
- in the late middle game it is very possible for groups to die, since the context is of positions that have become much more solid;
- the early endgame has some qualitative differences (thick plays, slow-moving attacks on weak groups) from the late endgame, in which every play can probably be counted precisely.
B: By opening
This isn't really an effective way to classify, though there are perhaps such things as 'typical Takemiya sanrensei positions'. Ryojimari positions are fairly characteristic.
C: By middle game features
This, in contrast, probably does help. For example suppose there is no large framework. Then the game has become a 'game of small groups'. This type of game is normally won by the player with better reading, so it is best avoided (unless you are strong).