Re: review of ldp-paging

On 07/24/2014 10:59 AM, John Arwe wrote:
> Sandro, what behavior did you have in mind if we added your unless 
> clause?
>
> As you can tell from my response (if you squint a bit), I read your 
> intent to be "if the container is sorted, the server is [probably: has 
> to] add a page anywhere in the sequence [in order to maintain the 
> sorting constraint it advertised], or to 410 the sequence" and it's 
> the first part that my response was concerned with.  If you had in 
> mind that the server Must abandon the sequence if it adds a page other 
> than at the end, that's not nearly as problematic for clients.
>

Sorry, I can't see the difference between your options.

I think we're saying there are three things a server is allowed to do 
when container gets a new member during paging, and the servers MUST do 
one of these three:

1.  Add the new item at the end.   That is, update the contents of the 
rel=last page, or start a new rel=last page.

2.  Add the new item on the page where it belongs according to the 
declared sort order.

3.  Reply with 410 gone.

The only design that's making sense to me is that unsorted containers 
MAY do either 1 or 3 and sorted containers MAY do either 2 or 3.  It 
makes no sense for unsorted to do 2, and sorted MUST NOT do 1.

Do you agree with all that?

Can you rephrase your question in that framework?   Or say what I'm missing?

       -- Sandro


> > > 4. adding at the end
> > > pages to the end.  Can we add, "unless some other ordering is 
> signalled,
> >
> > I never read 4's topic to be connected to sorting - ever, at all;
> > completely orthogonal concerns in my mind.  I thought the point of
> > the constraint on adding pages was to give the client a predictable
> > way to detect if more pages had been added (keep re-fetching last
> > page known to it and looking for either 4xx or link rel='next' to
> > show up in the response).
> >
> > I agree that makes adding pages into a server-sorted container
> > potentially impossible (in the sense of doing so by adding the
> > rel=next link), but I took that effective constraint as simply a
> > consequence of the functional composition.  If you relax the
> > constraint for sorted containers, for those you're rendering 4's
> > constraint useless; either way you're saying, in effect, that they
> > don't play nice together.  Given that the result is the same, I'm
> > pretty agnostic as to whether we treat that as a "club the baby
> > seal" moment or not.  The more pages in the sequence, the less that
> > allowing pages to be added anywhere helps a client, AFAICS; instead
> > of re-fetching 1 page the client would have to re-fetch all pages in
> > order to 'poll' for new ones, which is not meaningfully different
> > from traversing anew.
>
> Best Regards, John
>
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