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Fwd: Discussion of Blob URI Scheme for Binary Data Access | IETF

From: Noah Mendelsohn <nrm@arcanedomain.com>
Date: Sat, 14 May 2011 17:51:30 -0400
Message-ID: <4DCEF962.9030803@arcanedomain.com>
To: "www-tag@w3.org" <www-tag@w3.org>
CC: Arun Ranganathan <arun@mozilla.com>, Mark Nottingham <mnot@mnot.net>
FYI, from the uri@w3.org mailing list. Discussion should be held there, I 
think, at least for now.

Noah

-------- Original Message --------
Subject: Discussion of Blob URI Scheme for Binary Data Access | IETF
Resent-Date: Fri, 13 May 2011 18:09:08 +0000
Resent-From: uri@w3.org
Date: Fri, 13 May 2011 14:05:39 -0400
From: Arun Ranganathan <arun@mozilla.com>
Reply-To: arun@mozilla.com
Organization: Mozilla Corporation
To: uri@w3.org

Greetings URI listserv!

I'm writing to this listserv at the behest of Mark Nottingham, who sent
me here from the ietf-http-wg@w3.org listserv. This email is about a
"new" URI scheme used to access binary data, and we'd like feedback on
it, as well as advice on whether any further standardization endeavors
are necessary.

My name is Arun Ranganathan, and I'm the current editor of the File API
[1] specification (sometimes called the HTML5 File API, which is
unfortunate); I'm also the former Chair of the WebGL Working Group [2]
(which brings hardware-accelerated 3D graphics to the web), and have a
continued interest in allowing binary data to be securely accessed and
manipulated on the web.  I'm sponsored by Mozilla.

The File API introduces the notion of a Blob object [3], which
represents immutable binary data.  A file from the underlying file
system can be asynchronously read as a Blob object into various data
formats, for example.  The existing File interface in JavaScript
inherits from Blob.

Additionally, and most significantly for this listserv and this
discussion, the File API introduces a URI scheme for Blob access [4].
The URI scheme uses a subset of the HTTP status codes, and is designed
to be used wherever http URIs can be used within HTML markup and within
APIs in JavaScript (e.g. for "img src =", alongside XMLHttpRequest,
etc.).  The nascent URL API [5] which coins and revokes blob: URIs is
also used with the Stream API [6] for video-conferencing use cases, and
thus this scheme is becoming integral to emerging technologies under the
broad aegis of HTML.

Browsers such as Chrome already implement blob: URIs [7]; Firefox's
implementation will follow-suit, although is likely to be
vendor-prefixed.  Our goals are to address the shortcomings of the
file:/// URI scheme, which many browsers support for directory browsing
of the underlying file system, but for little else (file:/// URIs are
unwise choices for APIs like XMLHttpRequest, don't supply response
codes, etc.).  The blob: scheme was designed to address the use case of
dereferencing files and binary data on the web safely, since data: URIs
have shortcomings as well, and can't really be used for streams of data.

We'd welcome your feedback, including suggestions about whether
embarking upon an IETF standardization track for this protocol is
necessary.  The File API will soon be initiating a CFC for Last Call status.

-- A*

[1] File API: http://dev.w3.org/2006/webapi/FileAPI/
[2] WebGL: http://www.khronos.org/webgl/
[3] Blob defintion: http://dev.w3.org/2006/webapi/FileAPI/#dfn-Blob
[4] blob: URI scheme: http://dev.w3.org/2006/webapi/FileAPI/#url
[5] URL API: http://dev.w3.org/2006/webapi/FileAPI/#creating-revoking
[6] Stream API:
http://www.whatwg.org/specs/web-apps/current-work/multipage/dnd.html#stream-api 


[7] Use of blob: URI scheme in demos:
http://www.html5rocks.com/tutorials/workers/basics/#toc-inlineworkers-bloburis
Received on Saturday, 14 May 2011 21:51:55 GMT

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