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Re: Comments on proposed editor's draft of XBL2 from Forms WG

From: Adam Barth <w3c@adambarth.com>
Date: Wed, 22 Sep 2010 19:53:35 -0700
Message-ID: <AANLkTi=NtSwBm=XPa36XO0GZ8p1af2pVpv2LW6Nkqki6@mail.gmail.com>
To: "Leigh L. Klotz, Jr." <Leigh.Klotz@xerox.com>
Cc: public-webapps@w3.org
Perhaps the new effort should be called XBL3?


On Wed, Sep 22, 2010 at 9:30 AM, Leigh L. Klotz, Jr.
<Leigh.Klotz@xerox.com> wrote:
> A version of this message was previously sent by W3C Team request to a
> members-only list.
> At Art Barstow's request, I am sending the message to public-webapps, with
> all members-only content removed and all technical comments preserved.
> I have also corrected one typo, where "XForms" was typed in place of "XBL".
> This message is in response to
>   http://lists.w3.org/Archives/Public/public-forms/2010Sep/0005.html
> which reads in part
>    Since XBL2 wasn't getting much traction, I've taken an axe to the spec
> and
>    made a number of changes to the spec based on some discussions with some
>    browser vendors:
>       ...
>    The main changes are simplification: I've dropped namespace support, made
>    it part of HTML rather than its own language, dropped<style>
> and<script>
>    in favour of HTML equivalents, dropped all the<handler>   syntactic sugar
>    (and redirected event forwarding to internal object instead), dropped
>    <preload>, dropped mentions of XForms and XML Events, and so on.
> As co-chair of the W3C Forms WG and representative to that group from
> Xerox, I have been directed [W3C Forms WG Direction] to write the
> following comments to HCG:
> XBL is a successful component technology which allows declarative markup
> to be bound to implementations, and allows the implementations
> themselves to recursively consist of declarative and eventually
> imperative and user-agent-specific components.  It thus provides for
> declarative expressive power while still retaining the "unobtrusive"
> aspects of separate implementation.
> One widely-deployed implementation of XBL is in Firefox.  XBL in Firefox
> is widely used, but is non-standard.  XBL2 is an attempt to standardize
> XBL.
> We applaud the desire of the HTML5 WG to incorporate aspects of XBL into
> HTML5.  Even if it is reduced from XBL and XBL2, having such facilities
> in HTML5 will still help others using layered implementation technology
> of which HTML5 is one part (viz. [Ubiquity XForms], [Web Backplane],
> [XSLTForms]).
> One of the benefits of a W3C Recommendation is that the technology thus
> developed can have uses beyond its initial crucible.
> For example, at least two XForms implementations make use of XBL, and
> a third shows that it can be used alongside.
> In these cases, XBL is used to develop components and custom controls
> for XHTML, some using XForms but some not.
> We applaud the desire of the HTML5 WG to incorporate aspects of XBL into
> HTML, we ask that the HTML5 WG implement their own profile of XBL, and
> the XBL2 Rec-track document not be changed to include the proposed
> editor's changes removing XML namespaces, XML events, and other XML
> features from the XBL2.
> Uses of XBL in XForms and XHTML+XForms:
> 1. The XForms Wikibook [XForms Wikibook Custom Controls] community
> documentation shows a number of use cases for custom and aggregate
> controls with XHTML+XForms, most of which center around the Firefox
> implementation, but additional work is currently being done for other
> implementations such as Orbeon.
> 2. Mozilla Firefox [Firefox Custom Controls] documents how to write
> custom controls using Mozilla XBL.
> Additionally, much of the Mozilla XForms XPI itself is implemented using
> Mozilla's XBL.
> Namespace and other support is already present in XBL in Firefox;
> tetaining it in XBL2 would make it easier for such component
> technologies to be implemented cross-browser.
> 3. Orbeon uses a profile of XBL2 [Orbeon] to create components in their
> XHTML+XForms product.  Their use case requires namespace support.  They
> have a few additions to XBL2, notably parameters.  Orbeon has indicated
> they have a number of concerns about some of the details of XBL2, and
> that they are additionally not using all of it.  However, the parts they
> are using are the parts that the proposed editor's draft removes.
> 4. Xerox also uses a similar profile of XBL2 [Xerox], though somewhat
> reduced in features from Orbeon's implementation.  Xerox uses XBL2 as a
> transformation step in an XProc-like pipeline to instantiate complex
> controls in XHTML, both with and without XForms.  Xerox uses the
> parameter mechanism designed by Orbeon, but the implementation is different.
> In summary, please note that XBL technology has been in use as "glue"
> inside browsers for implementing XForms, has been in use in such
> browsers for components and extensions, and is also used for components
> in XHTML and XHTML+XForms implementations that have no internal use of
> XBL.  Retaining XBL2 as a Rec-track document is important for the Forms
> WG, because it can be used along with XForms, just as can XSLT and
> XProc, to great advantage.  Incorporating aspects of XBL into HTML5 is
> laudable, and we do not wish to hinder it, though we do point out that
> XML Event support is merely syntax for DOM Events, and that Namespace
> support is already present for XBL in browsers, so it would not seem
> that removing either is motivated by practical concerns.
> References:
> [W3C Forms WG Direction]
> http://lists.w3.org/Archives/Public/public-forms/2010Sep/att-0026/2010-09-15.html#topic11
> [Firefox Custom Controls Examples]
>  https://developer.mozilla.org/en/XForms/Custom_Controls_Examples
>  https://developer.mozilla.org/en/XForms/Custom_Controls
> [Orbeon]
>  http://wiki.orbeon.com/forms/doc/developer-guide/xbl-components-guide
>  No browser support is required.
> [Xerox]
>  At present, this is work in development for product release, but works
> with XSLT, XProc, and the AgenceXML XSLTForms XForms processor.
>  No browser support is required.
> [XForms Wikibook Custom Controls]
> http://en.wikibooks.org/wiki/XForms/Custom_Controls
> [XSLTForms]
> http://www.agencexml.com
> [Ubiquity XForms]
> http://code.google.com/p/ubiquity-xforms/
> [Web Backplane]
> http://webbackplane.com/
> Leigh L. Klotz, Jr.
> Co-Chair W3C Forms Working Group
> Xerox Corp.
Received on Thursday, 23 September 2010 03:50:24 UTC

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