I intend to go via Bank and then change on to the DLR. Do I need to swipe
at the DLR entrance ?

I thought that by swiping out at Canary Wharf, the correct fare would be
deducted.

I suspect there is a difference between what you are encouraged to do and
what actually will work in practice. Once upon a time when they had useful
information on the Oyster website you were encouraged to touch out and then
in again when switching between different modes of transport using PAYG.
Whether they considered DLR as separate to the Underground for these
purposes wasn't totally clear. However whether there has ever been a *need*
to touch out and in is another matter.

A sort of related example is at Farringdon where you can use PAYG on both
National Rail and the Underground. According to 'Ask Oyster' (I asked...)
the correct procedure when using PAYG for both legs of the journey is to
touch out on the Underground platform and then in again on National Rail (or
vice versa). However it has been suggested on this group that in practice
you don't need to use either.

Would it be so difficult to improve the signs above the validators to
explain the situation better?