Mobile Web Best Practices Working Group Teleconference

Allow and Disallow Lists

francois: I summarized the choices as I see them in the agenda, and I was wondering if this is a good picture
... we should wait for the new draft before deciding unless we can come up with a clear consensus now
... we have three choices (as discussed in the agenda)
... my personal preference would be for b), but are there any other points of view to take into account?

<francois> jo: I think we can step around this one actually, either with "unspecified means", either by saying "prior interaction with the server"

<francois> ... and then we can then leave that open

<francois> ... The important thing is IMO that the so-called algorithm is self-healing, and if we keep it this way, we don't really need to go in the like/don't like allow/disallow lists discussion

jo: I think we can avoid referring to specific internal mechansims by referring tot he notion of p"previous experience" and "a priori" knowledege, providing that the algorithm makes it plain that no matter what the proxy thinks it knows, but whatever means it thinks it knows it, it must act on the evidence that is presented by the server first and foremost
... we can gain consensus hopefully by focussing on mitigating the undesirable effects without prohibiting the use of them

heiko: two issues here ...
... role of allow and disallow list is one question, the other question is setting up an allow list for setting up a different user agent string
... the first issue is allow or disallow transformation the second is allow or disallow bogus user agent headers

francois: but not mentioning them surely avoids the issue

heiko: if you are allowed to bypass this is a different issue to no-transform
... we need to think about what we are allowing or disallowing

francois: allow lists to discuss the possibility of sending altered headers
... and the second to allow overriding cache control, two different uses of the list

seanp: one issue with b) is that it deals only with the response whereas one would need to look at such lists on the request
... there may be a disconnect as to what people are using such lists for now
... so if we mention at all we should make this clear

francois: actually I think b) only deals with the HTTP request to know if you have to send another one

<hgerlach> sorry I got a 2nd call will be back soon

seanp: if you have allow list you can send altered headers straight away
... you are saying that is the prior knowledge

francois: the point jo emphasised it that it makes sense to send altered headers straight way but it needs refreshing from time to time
... it really depends
... ithink we should postpone the decision till we see the new document

<Zakim> jo, you wanted to say that as a point of principle one should avoid mentioning internal mechanisms that are proprietary to the proxy

<francois> jo: Allow/Disallow are not really externally visible, so we should not step into the behavior of the Proxy, and not mention them. You can infer that there are such lists. we deal with the interactions between the server and the proxy

francois: suggest we leave it and move on

Persistent Expression of User Preferences

<francois> Jo's points commented by Sean and me

<Zakim> jo, you wanted to say that the algorithm referred to above should help with this too

<francois> jo: Thinks that it is linked to the algorithm. If we're clever, I guess we'll say that the proxy should prompt the user again when the response from the server differs from the previous one.

<francois> ... a bit woolly but we cannot do any better, I think.

jo: I think that the key point is that when a user has a persistent expression of preference we want to make sure that if a host changes its operation the user gets the chance to re-express their preferences
... and this requires the proxy maintain some kind of "prior knowledge"

francois: seanp can you clarify something from your email ... the origin server can tell that the request has passed through the CT proxy, if it changes its operation it can tell the CT proxy this by sending a 406 status with a vary header

seanp: basically the origin server can tell ... by looking at the X-Headers
... so it can determine that the server now does not want the CT proxy to do transformation any more
... so the CT proxy will know to not do transformation for that site any more
... I thought tha was why we had the point under 4.3 in here

francois: {mumbles}

seanp: origin server can tell that it is going through a proxy so what we need is for the origin server to show that is is now aware
... couple of cases one where is was aware and changes its mind, and the other is that it wasn't aware and now doesn't want transformation

francois: there we are using the response from the server as a direct communication with the proxy rather than having end-to-end significance
... the problem is that the 406 is not intended for the end-users

seanp: but surely that's what we do when it works the other way round

francois: but in that case it really is saying "I can't handle your device"
... in your illustration its the server telling the proxy to change its ways

seanp: sure but the practical results are the same

jo: not sure that what Seanp proposed doesn't require the server to know about tasting and prior requests, hope we can sweep this all together in a new draft
... I have put a placeholder for illustrations of interactions
... so we can make sure we have tested this all out

francois: anything else we need to sweep up
... trciky part is about cps that offer users a choice of representation
... and how to tell proxy that they are handling the choice themselves
... don't know if there are any technical possibilities, not sure we can decorate this any further
... anyone got a view on that?

jo: think that this is a problem and am hoping to find an answer!

<hgerlach> +1

francois: clarifying that it's best practice for the server to offer such a choice

heiko: server can offer a menu offering choices
... but this will require an additional database
... e.g. how to determine that there is a .mobi page for something that is not in the .mobi domain

francois: can advertise via the linkelement

heiko: how can can the proxy know that the pages exist
... how do they know where the mobile page is

francois: there are two things, the server can already tell the proxy that such pages exist using the link element, but the difficulty is telling the proxy that they also offer that choice in a user visible way
... there are a number of problems, e.g. that this may offer this at a site level, could be POWDER, but that is scope for future work

heiko: no there can be a database for that purpose even if the site owner has not set this information?

francois: what kind of database?

heiko: well there is the .mobi database

francois: the ct proxy could consult such a database?

heiko: yes

francois: there is no fixed relationship between domain names

seanp: there is lots of way to map between mobile sites and desktop sites and mobile sites and vice versa
... so this seems like a CT vendor issue
... if the page doesn't contain the issue then its a CT vendor issue

<Zakim> jo, you wanted to say that databases are out of scope

seanp: there are a million different ways of doing this, no algoritm as such

<francois> jo: out of scope, since we're talking about using HTTP. We should not refer specifically to any specific implementation mechanisms

jo: we shouldn't refer specifically to particular implementation mechanisms

francois: final issue ... CT proxies providing links to alternative representations ... I did include a Proposed Resolution, in the agenda but let's leave that one too
... for the time being

jo: hope to have new draft by tomorrow or by thursday

<hgerlach> -1 bye