W3C home > Mailing lists > Public > www-forms@w3.org > November 2006

Re: repeats

From: Mark Birbeck <mark.birbeck@x-port.net>
Date: Mon, 13 Nov 2006 15:35:48 +0000
Message-ID: <640dd5060611130735y2c16433boe7ef92d01192780a@mail.gmail.com>
To: "Erik Bruchez" <ebruchez@orbeon.com>
Cc: www-forms@w3.org

Erik,

I think Jason's point is very good, and it is exactly the same reason
I have been trying to get a bind function into XForms for ages.

His argument is basically that having that 'extra level of
indirection' is a bonus because it allows the data to move without the
UI having to change. I would totally agree with this, and can provide
a large number of forms that we have devised where we have created
generic 'patterns' where the UI sits atop a set of bind statements,
and then those bind statements map to specific data. This is crucial
for 'reuse'.

For example, when creating a form that makes a request to a server,
and then navigates the list of items returned, with 'next' and
'previous', etc., the mark-up is almost identical each time, with the
only difference being the XPath expressions to access the data.
Instead of having to edit XPath expressions in the UI, we can use bind
statements to create a UI that navigates a 'recordset', and then just
change the binds to suit different data.

XForms needs far more of this kind of stuff if it is to be reusable;
at the moment my guess is that many forms are hand-crafted,
artisan-style, but there is no reason that people shouldn't be able to
take my 'recordset' pattern and just drop it into their forms, and
then simply tweak the bind statements accordingly for their data.

Regards,

Mark


On 13/11/06, Erik Bruchez <ebruchez@orbeon.com> wrote:
>
> Jason,
>
>  > really?
>
>  > I haven't checked the detail of the new insert attributes - are you
>  > seriously saying that you cannot use a bind as an origin or context?
>
> The @origin and @context attributes are XPath expressions.
>
>  > If thats the case then its just another nail in the whole bind
>  > coffin I think - w3c folk - What is the point of creating binds if
>  > you cant use them anywhere?
>
> XForms uses different attribute names to refer to binds (@bind)
> vs. XPath expressions (@ref, @nodeset, @context, @origin). From that
> you can infer that @context and @origin must support either XPath, or
> bind ids. Currently, it's the former. What you would probably want is
> something like @context-bind and @origin-bind, but these attributes
> are currently not defined in XForms 1.1.
>
> This is good feedback for the working group though: I am not sure
> whether we have considered using binds for the functionality or
> @context or @origin so far.
>
>  > please consider this when designing this stuff because xforms is
>  > threatening to become a nightmare of xpath to manage.
>
> Well, that's a open debate. You want to use binds everywhere, but I
> usually don't use them much. So I for one don't have any problem at
> all writing:
>
>    @origin="instance('my-template')"
>
> That's simple and clear enough for me (but that's just me).
>
>  > Just think how painful it would be to add/remove/change any data
>  > structure in any big complex array of forms if they are just
>  > completely littered with xpath.
>
> That's probably subjective. Someone could argue that you are littering
> your form with binds ;-) Binds add an additional indirection, which
> has benefits but also drawbacks - like the fact that you add to the
> existing XPath "space" a new space of bind ids.
>
> (Digression: This reminds me of things like Java ant files: people
> always tend to write things like:
>
>    <property name="war.lib" value="${war.inf}/lib"/>
>
> Somebody could argue that sure, that's a valuable indirection, just in
> case someday you want to change where the WAR lib directory is, or
> where the WEB-INF directory is. The truth is that you are never going
> to move it, and that the indirection is fairly pointless: you will be
> as clear writing WEB-INF/lib instead of ${war.inf}/lib.
>
> This not to say that binds are useless, but that they may, in some
> circumstances, be just pointless indirections. End of philosophical
> digression.)
>
> -Erik
>
> --
> Orbeon Forms - XForms Everywhere
> http://www.orbeon.com/blog/
>
>
>


-- 
Mark Birbeck
CEO
x-port.net Ltd.

e: Mark.Birbeck@x-port.net
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Received on Monday, 13 November 2006 15:36:05 GMT

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