Expand sequence diagram

[judgej]

Sage Pay provide a sequence diagram showing the success path of a transaction. This is great for when things work first time.

What the diagram does not show, is the points and actions when session tokens and card identifiers expire (by time or by number of uses). In these cases the sequence is taken back to an earlier stage (preserving all user-entered data captured so far) so that tokens and identifiers can be renewed. At some points this will need data to be renetered by the user, in other places it won't.

[judgej]

The source was drawn up in Visio.

[judgej]

The sequence diagram has been long removed from the Sage Pay docs. It only showed the single success-path anyway, so was pretty useless to develop against.