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Re: Musings on PWP Offline/Online Modes

From: Leonard Rosenthol <lrosenth@adobe.com>
Date: Wed, 6 Jan 2016 11:01:54 +0000
To: Ivan Herman <ivan@w3.org>, Daniel Weck <daniel.weck@gmail.com>
CC: Brady Duga <duga@google.com>, Dave Cramer <Dave.Cramer@hbgusa.com>, "Nick Ruffilo" <nickruffilo@gmail.com>, Tzviya Siegman <tsiegman@wiley.com>, Charles LaPierre <charlesl@benetech.org>, W3C Digital Publishing IG <public-digipub-ig@w3.org>
Message-ID: <5A1B9C8B-F5F5-4600-ACE6-C0B2003F8AC9@adobe.com>
For any PWP, just as with a web site, there needs to be a “base URI” from which all relative URIs are resolved.  It is also the scope/root/origin domain when considering cross-origin requests. 

As such, I would certainly expect that for the case of a “fully self-contained” PWP, that all URIs are exist as relative to that origin/base.   For any PWP that wants to reach out to external resources, then it can do whatever it wants (modulo CORS or other issues).

Again, as with other things, let’s not let specific implementations or separate discussions (such as the BFF - browser friendly format) influence the general purpose definitions of a PWP and its RS.  We, of course, should insure that we don’t prevent such things.

Leonard



On 1/6/16, 5:28 AM, "Ivan Herman" <ivan@w3.org> wrote:

>Hi Daniel,
>
>> On 6 Jan 2016, at 11:16, Daniel Weck <daniel.weck@gmail.com> wrote:
>> 
>> Hi Brady,
>> Service Workers can intercept resource requests via "fetch" event
>> listeners, as long as the URLs originate from within the permitted
>> scope (which is itself an HTTPS URL). So in fact, intercepting
>> requests to "external" resources is not possible (i.e. different
>> domain, or even just URL path outside of the registered scope). Note
>> that the "fetch" *API* (not the event type) can of course be used to
>> programmatically emit requests to resources hosted on different
>> domains (via HTTP CORS, just like XmlHTTPRequest), and this can indeed
>> be used to populate a cache, or to build a PWP / EPUB zipped package
>> based on some predefined manifest (i.e. list of well-identified
>> publication resources).
>
>Just for my understanding: does it meant that, for a specific PWP, the (SW based) RS has to 'register' a number of domains or URL-s in its scope in order to be able to catch the requests and cache the content? If so then, in practice, we are close to the idea that a GET to a PWP should return (some form of) a manifest with the resources the PWP contains which should then be "registered" by the RS.
>
>What bothers me a bit is that, in [1], it talks about *a* 'scope URL'. Does it mean that, by default, the URL-s that are used by a PWP should all be under the same, fixed scope, and we must have a redirection mechanism built in to provide an access to external resources (using the fetch API)?
>
>This does have to shape our thinking, if this is all true.
>
>Thanks
>
>Ivan
>
>[1] http://www.w3.org/TR/service-workers/#dfn-scope-url

>
>> 
>> References:
>> 
>> http://www.w3.org/TR/service-workers/#dfn-scope-url

>> 
>> https://github.com/jakearchibald/ebook-demo/blob/gh-pages/publisher-site/sw.js

>> 
>> https://github.com/jakearchibald/ebook-demo/blob/gh-pages/reader-site/sw.js

>> 
>> Regards,
>> Daniel
>> 
>> On Tue, Jan 5, 2016 at 4:39 PM, Brady Duga <duga@google.com> wrote:
>>> One thing to note regarding service workers - while they can be used to
>>> cache in this simple case of an image on a different server, I don't think
>>> they could be used in a more complicated case where resources identify other
>>> resources. So, if you make a page of your publication be
>>> http://louvre.com/monalisa.html, which in turn references
>>> http://louvre.com/monalisa.jpg I don't think it is possible to cache the
>>> image. Though, I am not an expert on service workers, so my understanding
>>> could be flawed.
>>> 
>>> On Tue, Jan 5, 2016 at 7:44 AM, Ivan Herman <ivan@w3.org> wrote:
>>>> 
>>>> I think the goal should be somewhere in the middle. I agree that the
>>>> definition of PWP should be, as much as possible, implementation agnostic,
>>>> but I agree with Dave that saying "we don't care" is also not appropriate.
>>>> 
>>>> We may have to define a PWP Processor in the abstract sense. What a
>>>> processor is supposed to do to answer to different use cases, what are its
>>>> functionalities, that sort of things. We may not define it in a normative
>>>> way in the sense of some formal language or terminology, but we have to
>>>> understand what can, cannot, should, or should not be done with a PWP. And
>>>> it is certainly important to know whether the realization of such a PWP
>>>> processor is possible with today's technologies, what is PWP specific and
>>>> what can be reused off the shelf, etc.
>>>> 
>>>> Ivan
>>>> 
>>>> 
>>>> On 5 Jan 2016, at 16:24, Cramer, Dave <Dave.Cramer@hbgusa.com> wrote:
>>>> 
>>>> On Jan 5, 2016, at 9:41 AM, Leonard Rosenthol <lrosenth@adobe.com> wrote:
>>>> 
>>>> Nick – the specifics of how an RS chooses (or not) to cache are out of
>>>> scope for PWP.  They may make sense for some sort of format-specific work
>>>> (eg. best practices for PWP with EPUB) but we don’t care about it here.
>>>> 
>>>> Remember – PWP is format/packaging and implementation agnostic.   (we
>>>> seemed to all agree to that pre-holidays)
>>>> 
>>>> 
>>>> The fact that an existing web technology can solve a critical use case for
>>>> PWP is on-topic in my opinion, and learning about such things can only help
>>>> our work. Such technologies may not be a part of the documents we produce,
>>>> but saying "we don't care about it here" I think sends the wrong message.
>>>> 
>>>> Dave
>>>> This may contain confidential material. If you are not an intended
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>>>> 
>>>> 
>>>> 
>>>> ----
>>>> Ivan Herman, W3C
>>>> Digital Publishing Lead
>>>> Home: http://www.w3.org/People/Ivan/
>>>> mobile: +31-641044153
>>>> ORCID ID: http://orcid.org/0000-0003-0782-2704
>>>> 
>>>> 
>>>> 
>>>> 
>>> 
>
>
>----
>Ivan Herman, W3C
>Digital Publishing Lead
>Home: http://www.w3.org/People/Ivan/
>mobile: +31-641044153
>ORCID ID: http://orcid.org/0000-0003-0782-2704
>
>
>
>
Received on Wednesday, 6 January 2016 11:02:30 UTC

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