[Ur] Generalizing transactions

[Adam Chlipala]

Karn Kallio wrote:
> Adam, now that somebody ( Marc Weber ) is working on an application ( payment
> gateway ) where the transaction model of Ur/Web does not cleanly apply, is
> there a chance of you generalizing Ur/Web transactions in a safe, principled
> way ( that allows representing the semantics of the application's effectful
> operations within Ur/Web )?  For example, I think that the problem of leaving
> a permanent record of an event ( e.g. receiving an order and not removing it
> on failure rollback ) could be handled with a SAGA that has a null
> compensation for the process of writing the record.
>    

It seems like Marc and I have settled on a very straightforward and 
not-ugly way of implementing what he wants, so this case doesn't seem to 
me like a good impetus to add a new fancy feature.  I'm perfectly happy 
to help you figure out how to implement it yourself, if you want. :-)