In this section, we will take an example from ECommerce order process, to understand the state transitions involved. Lets see what happens when a "user" buy some products from a ECommerce site.
Scenario
User picks some products to his shopping cart, proceed to checkout page, and click the confirm button to make the order "Confirmed". The user is re-directed to the payment providers page, where he enteres payment details, and when the payment process finishes, the order is "Paid", the amount of money is collected from the user, who now has become a "customer"!.
If you look at the above scenario, you will quickly see that, order "Processing" doesn't really end there!. There is more to it.
Now, the involvment of the customer is over as far as the ECommerce public site is concerned. But the seller has to look at the order, package the items bought and should get a delivering company to get those items "Delevered" to the customer.
After delivery the seller should get some kind of a confirmation (in a normal scenario) and only then the order can be "Closed". If the delivery could not be made, then its delivery should be "Failed", and this order need to be "Cancelled", and payment amounts "Returned" to the user.
Just return back to above two paragraphs and note the following words in bold quotation marks. "Confirmed", "Paid", "Processing", "Delevered", "Closed", "Failed", "Cancelled", "Returned". What do these words describe?
They describe a "State" the order as a whole is in, in a given time. Also note that they are in a particular sequence, one state comes after the other.
Also note that, based on your implementation project, such states recognized in order processing will defer. For example, some implementations would allow a state called "Partially Delevered", etc.
We can represent the scenario in a diagram as follows:
Though it looks pretty simple and straight forward, we will need a more precise and formal way of handling the above sitation when we are trying to automate it into a computer application. That is exactly what Litium Studio State Transition System is doing: Formalizing and representing states and its transitions in ECommerce order processing.