8.7. Natural conversation IDs

When working with conversations that deal with persistent objects, there are several reasons to use the natural business key of the object instead of the standard, "surrogate" conversation ID.

Easy redirect to existing conversation

If the user requests the same operation twice, it can be useful to redirect to an existing conversation. Take the following situation, for example:

You are on Ebay, halfway through paying for an item you won as a Christmas present for your parents. You want to send it straight to them, but once you have entered your payment details, you cannot remember your parents' address. While you find the address, you accidentally reuse the same browser window, but now you need to return to payment for the item.

With a natural conversation, the user can easily rejoin the previous conversation and pick up where they left off. In this case, they can rejoin the payForItem conversation with the itemId as the conversation ID.

User-friendly URLs

A user-friendly URL is meaningful (refers to page contents plainly, without using ID numbers), and has a navigable heirarchy (that is, the user can navigate by editing the URL).

With a natural conversation, applications can generate long, complex URLs, but display simple, memorable URLs to users by using URLRewrite. In the case of our hotel booking example, http://seam-hotels/book.seam?hotel=BestWesternAntwerpen is rewritten as http://seam-hotels/book/BestWesternAntwerpen — much clearer. Note that URLRewrite relies upon parameters: hotel in the previous example must map to a unique parameter on the domain model.