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Re: CFC: Getting rid of 'extras'

From: Greg Billock <gbillock@google.com>
Date: Wed, 22 Aug 2012 16:07:37 -0700
Message-ID: <CAAxVY9cDs9xgVSObVcq3vPicSaEP+8TU06firi5pG9rL1sFNXw@mail.gmail.com>
To: James Hawkins <jhawkins@google.com>
Cc: WebIntents <public-web-intents@w3.org>
Definitely. The big driver for extras was MIME types, so here's a MIME
type before:

type: image/png
data: blob = image contents
extras: { "url" : image url,
            "filename" : representative filename,

and a proposal for a format with no extras:

type: image/png
data: { "blob" : blob image contents,
          "url" : url of image contents,
          "filename" : representative filename,

Using a map as a recommended base type for data provides a lot of
flexibility. It provides an open namespace into which new optional
features can be placed to satisfy new use cases as usage evolves. A
goal will be to create a consistent vocabulary across types, so for
example "url" means "a url pointing to the content" for all MIME

On Wed, Aug 22, 2012 at 3:44 PM, James Hawkins <jhawkins@google.com> wrote:
> Can you provide an example to show before and after?  A few disparate cases
> would be helpful to see the impact of the change.
> Thanks,
> James
> On Wed, Aug 22, 2012 at 2:09 PM, Greg Billock <gbillock@google.com> wrote:
>> In June, we discussed getting rid of getExtra() in favor of an extras
>> attribute (i.e. [1]). I'm increasingly persuaded that we should just
>> get rid of extras altogether. When this was proposed [2], it was
>> because we knew we needed to be able to attach metadata to the payload
>> data for pre-existing types (such as MIME types). But a better scheme
>> to deal with that is to create extensible payload formats to begin
>> with. Such formats have to be documented anyway (see e.g. [3]), and so
>> it is better to just use the existing structured-clone payload to
>> describe the type. Any extra header information can just be included
>> there.
>> So the proposal is to strike |getExtra()| from the API, and add a best
>> practices recommendation that any documented payload type passed
>> through |data| be a Javascript Object type so that fields may be added
>> to it as necessity arises.
>> This would mean a revision to documents such as [3], but going forward
>> it puts data passing on a firmer footing where types get designed with
>> extensibility in mind from the beginning. I don't think we even really
>> lose any generality -- web developers need to consult documentation to
>> figure out which extras keys mean what, anyway, and as we've learned
>> from trying to pass MIME types, there end up being reasons to want to
>> pass, say, both URLs and Blobs through the type anyway, not to mention
>> even better future constructs, such as Stream [4], so there isn't much
>> intuitive power in the type anyway. If you have to consult the
>> documentation, it's easier to document the type as one object, rather
>> than as the object and then extras data.
>> [1]
>> http://lists.w3.org/Archives/Public/public-web-intents/2012Jun/0118.html
>> [2]
>> http://lists.w3.org/Archives/Public/public-web-intents/2012Mar/0003.html
>> [3] http://www.w3.org/wiki/WebIntents/MIME_Types
>> [4] http://dvcs.w3.org/hg/streams-api/raw-file/a3858f3ef0ae/Overview.htm
Received on Wednesday, 22 August 2012 23:08:05 UTC

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