[ Tino Wildenhain]
This semantic you are referring to is effectively non existent. Sorry. If you see real world examples there are a lot of cases where the information indeed changes between GET requests.
I am not disputing that there are plenty of real-world cases where the designer paid no attention to the intended semantics. I am saying that, given a choice - and you have one if you are developing a system - it is a good idea to follow the intention rather than to deliberately go against it.
See for example the shop, where you put items in a backet. On each page there is the number of items currently in the basket displayed. So no matter if you put it in via GET or POST at least another GET will give you different result. Its just not feaseable to do it any other way (e.g. only use POST for modifying data)
I do not see this at all (I mean, the "not feasible" part). You are building the page, and whether you have your server stick the information into a query string that is the value of a form's ACTION attribute, or somewhere else in the form is up to you - you get to choose how to do it. One way is as easy for the server as the other. Anyway, a GET is of course allowed to give different results, just not because of something that happened *because* of the GET. The GET is supposed to reflect the current state of the thing, and if the state were to change, so would the results of a GET, as Toby also mentioned. None of these considerations need have anything to do with the html that displays the contents of a shopping cart, or with a query string used with a GET. Cheers, Tom P