Re: DataCache API - editor's draft available

On Jul 21, 2009, at 9:15 PM, Adrian Bateman wrote:
>
> I don't think the problem is that we couldn't build yet another  
> cache that is similar but different to the AppCache that others are  
> already shipping so I don't think a reference implementation is the  
> solution. I think the problem is motivation - are there any use  
> cases that adding DataCache enables that couldn't otherwise be  
> implemented with what we already have and are those compelling  
> enough to complicate the platform with another cache mechanism.  
> Further, would we end up with conflicts between the AppCache and the  
> DataCache since they're currently not unified as far as I can tell.

[...]

> What I'm asking for is a more unified proposal that says "If you  
> have already implemented AppCache, here's what you add to make the  
> same cache provide the additional functionality needed to enable  
> these additional use cases." This will inevitably be a compromise  
> from what a pure implementation looks like (your current DataCache  
> spec, say) but lots of the web is necessarily a compromise because  
> it builds on prior art that might not have been ideal but has been  
> specified, built and deployed (and not always in that order).

This is pretty close to my own point of view. I think the  
functionality offered by DataCache is interesting, but I'd be much  
more interested in putting it into Safari and WebKit if it was exposed  
as a set of extra AppCache features, rather than a competing and  
unintegrated separate model.

I believe AppCache can reasonably be extended to support the extra  
functionality of DataCache. For example, it should be possible extend  
the manifest format with a way to express that a certain URI should be  
served by script, and to give that script access to a static cached  
copy if it chooses to use it.

> This would allow people to form a judgement about whether the  
> additional use cases are worth the additional effort instead of  
> whether the additional use cases are worth yet another cache. I  
> think the ship has already sailed on AppCache and we can't undo that  
> even if we wanted to and I don't think a competing solution is the  
> right approach.

I agree with this as well. I think extending AppCache is likely to be  
a more successful approach than building a full alternative. I will go  
further and say that if some of the advanced DataCache features were  
expressed as extensions AppCache, we would likely be very interested  
in implementing them.

Regards,
Maciej