[whatwg] A thought: <a href="..." method="post">
jg307 at cam.ac.uk
Fri May 13 14:02:24 PDT 2005
Kornel Lesinski wrote:
> On Fri, 13 May 2005 16:56:44 +0100, James Graham <jg307 at cam.ac.uk> wrote:
>> That seems to be based on the belief that all things which look like
>> links must correspond to idempotent actions.
> Yes, that is exactly the idea behind it.
>> I don't think this is true and, in general, think that trying to
>> couple the user interface to the underlying protocol is a bad idea.
> That is user interface which represents what protocol does.
> Links are not coupled with http GET method. You may link to any
> resource using any protocol, but following a link should not have
> side-effects - by design.
> Web applications usually don't have undo, so IMHO it should be clear
> that click on certain UI elements has side effects.
But that's already unclear. Given a button on a web page it's impossible
(without context) to tell if it has side effects or not. If I click the
"Search" button on Google, it has no side effects yet the "Submit Order"
(or whatever the exact working is) button on Amazon, despite being
exactly the same type of UI element, has side effects. The same is true
in offline UIs - the Save menu item in my text editor is non-idempotent
yet the close-by Open menu item is idempotent. In general, it's hard to
think of a class of UI where it's unambiguous which actions will have
side effects just from the visual presentation of the elements and
without additional contextual information.
Despite this, people have the desire to make links a special class of UI
object that correspond to idempotent actions only. From a purely
mechanical point of view, this makes sense - after all one doesn't want
bots to follow links. From the point of view of that part of the web
that consists of interlinked documents it mostly makes sense. But from
the point of view of web applications, it doesn't make sense. It makes
no sense to require a webmail application to use a form element to open
each message just because doing so modifies the underlying database,
despite the fact that a link is an appropriate element to represent the
Fortunately for the UI designers, there is an acceptable alternative to
there was a way to ensure that links were _never_ used for
non-idempotent actions, you'd still see link-like elements used for such
actions. Unfortunately they'd have none of the semantic value offered
by <a> elements.
"But if science you say still sounds too deep,
Just do what Beaker does, just shrug and 'Meep!'"
-- Dr. Bunsen Honeydew & Beaker of Muppet Labs
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