t; B         |
|         |                   | on dA             |                   |
o---------o-------------------o-------------------o-------------------o
| dA%     | [d!A!]            | Tangent universe  | (D^n, (D^n -&gt; B)) |
|         | (dA, dA^)         | at a point of A%, | (D^n +-&gt; B)       |
|         | (dA +-&gt; B)        | based on the      | [D^n]             |
|         | (dA, (dA -&gt; B))   | tangent features  |                   |
|         | [da_1, ..., da_n] | {da_1, ..., da_n} |  