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Re: Fixing appcache: a proposal to get us started

From: Julian Reschke <julian.reschke@gmx.de>
Date: Thu, 25 Apr 2013 17:06:23 +0200
Message-ID: <5179466F.4020505@gmx.de>
To: Jonas Sicking <jonas@sicking.cc>
CC: James Graham <jgraham@opera.com>, public-webapps@w3.org
On 2013-03-27 01:20, Jonas Sicking wrote:
> On Tue, Mar 26, 2013 at 1:48 AM, James Graham <jgraham@opera.com> wrote:
>> On 03/26/2013 08:02 AM, Jonas Sicking wrote:
>>> Another "feature" that we are proposing is to drop the current
>>> manifest format and instead use a JSON based one. The most simple
>>> reason for this is that we noticed that the information we need to
>>> express quickly became complex enough that using a format with simple
>>> parsing rules was beneficial.
>>> A format based on extending the current appcache format would be no
>>> problem for a UA to parse. However the complexity that we need to
>>> express resulted in something that's too hard for a human to manually
>>> write, or for a human to understand when looking at somebody else's
>>> manifest in order to learn.
>>> The simple parsing rules for JSON seemed like a better fit. It also
>>> provides more of an opportunity to extend the format in the future.
>>> JSON also has advantages when it comes to creating APIs exposed to
>>> webpages for interacting with appcaches. More about this below.
>> Some slightly trivial feedback: I am worried about using a format with no
>> support for comments. I agree that some hypothetical JSON+comments format
>> would be a good fit, but without the ability to document complex rulesets,
>> it seems like we are going to create a maintenance nightmare.
> I completely agree. I feel like we're stuck between a rock and a hard
> place here.
> On one hand we need something that supports comments. JSON only
> "supports" comments using ugly hacks like:
> {
>    "//": "Remember to update this as needed",
>    "version": "2",
>    "//": "Need nav.css for sidebar",
>    "cache": ["index.html", "index.css", "nav.css"]
> }
> On the other hand, using something other than JSON means that we loose
> the ability to use existing tool chains for processing the manifest.
> I'm not so worried about the UA having to write new code in order to
> implement the AppCache feature itself. I'm more concerned that
> serverside code that wants to process the manifest can't use a normal
> JSON parser, and that client-side code that wants to load a manifest
> can't use things like xhr.responseType="json".
> I really don't know which downside is worse.
> I definitely wish that JSON supported comments, but that doesn't seem
> likely to ever happen :(
> ...

Well, there is a format with good server and client support that allows 
comments. It's called XML.

Best regards, Julian
Received on Thursday, 25 April 2013 15:06:55 UTC

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