??? so consider ... ?? affine plane with origin blown up .... ???? ....

?? affine plane ... k[x,y]

k[x,y:0; a,b:1]/ay=bx .... ?????....

(?? presentation as "computer program"-like ??? ...)

?? exact sequence .... ??

-> /ay=bx -> Z ... ???

?? morally qualify as "short exact" ... ??????? ..... ???? .....

?? fiber over j ... ????....

??? wait a minute .... for negative j the fiber is empty, right ???? .....

... hmmmm .....

?? need to draw a picture ..... ?????? ........



???? .....

??? short exact sequence with base N instead of Z ??? .....

??? so ... ??? consider .... X ... = .... ???? with grading given by ... ??? ??? _is_ this exactly "rees" construction ??? .... ????.... filtration .... to grading ... ????.... ??? .....

?? ????? ........ ?????......