On 2 September 2015 at 12:55, Dave Cridland <[email protected]> wrote:
> (Matthew Miller prodded me that I hadn't replied to this). > > On 18 August 2015 at 12:39, Ben Langfeld <[email protected]> wrote: > >> On 18 August 2015 at 08:13, Dave Cridland <[email protected]> wrote: >> >>> >>> >>> On 17 August 2015 at 20:15, Ben Langfeld <[email protected]> wrote: >>> >>>> >>>> >>>> On 17 August 2015 at 13:44, Kevin Smith <[email protected]> wrote: >>>> >>>>> On 14 Aug 2015, at 20:11, Ben Langfeld <[email protected]> wrote: >>>>> > > 2) 5.1 (Actors) places requirements that these JIDs for >>>>> components/mixers can only be only be under subdomains - why is this? >>>>> AFAIK, this is the only part of XMPP that implies any relationship between >>>>> a domain and a subdomain, and it doesn’t immediately seem like a useful >>>>> restriction. >>>>> > > >>>>> > > Not true. The word I used was "perhaps". This is simply to point >>>>> out that full JIDs must be used to address these entities and no >>>>> relationship between domains may be assumed. >>>>> > >>>>> > I think that at least the table in 5.2 is quite explicit in >>>>> requiring things to be a subdomain - I take it this wasn’t intended. >>>>> > >>>>> > Actually quite the opposite: >>>>> > >>>>> > > where elements in square brackets are optional >>>>> > >>>>> > <call ID>@[<call sub-domain>.]<service domain>/<component ID> >>>>> > >>>>> > Quite explicitly optional, I'd say. >>>>> >>>>> Sorry, badly expressed. It is optional that it’s a *sub*domain, yes. >>>>> But if it’s not the service domain, you’re requiring it to be a subdomain >>>>> of the service domain. This is what I was calling out - this is a unique >>>>> requirement in XMPP; there’s usually no formal relationship between >>>>> different domains like this, and it’s not clear to me that one is needed >>>>> here. >>>>> >>>>> >>> I'd like to see the answer to this one. Given a server of >>> shakespeare.lit, do I understand that a call must be within either that >>> domain or a subdomain of it? >>> >> >> I guess that's what this implies. I have yet to hear why it's a bad thing >> though. >> > > Because nothing else relies on this relationship in XMPP. Domain names - > whether "subdomains" or not - do not have any relationship, implied or > otherwise. > > So in order to mandate this, you really need to come up with an > overwhelming reason why this specification should require this, unlike > every other XMPP specification. > Ok. I'll see what I can do to remove that stipulation from the text. AFAIK it won't make any technical difference, it's just a logical thing. > > > 5) 6.1 - if you want to rely on presence here, isn’t an unavailable >>>>> presence the best way to signal unavailability? I don’t think it’s covered >>>>> what receiving unavailable would mean here at the moment. >>>>> > > >>>>> > > See above. >>>>> > >>>>> > I think at least the second part of the question stands - what does >>>>> receiving unavailable mean? >>>>> > >>>>> > Means that the client has gone offline and will not interact with >>>>> the calls under its control any more. The Rayo server may choose to hang >>>>> up >>>>> those calls, wait for the client to come back, or any other >>>>> implementation-specific behaviour. >>>>> >>>>> It seems worth mentioning this, to me. >>>>> >>>>> > > 8) 6.2.1 How does the client discover the available URI schemes >>>>> for to/from? >>>>> > > >>>>> > > No such discovery is specified, and it is assumed that a Rayo >>>>> service would document this. >>>>> > >>>>> > It’s not clear to me what this means for interoperability. Does it >>>>> mean that one can’t implement a Rayo client using this XEP and expect it >>>>> to >>>>> interoperate with an arbitrary Rayo service, because it won’t know what >>>>> the >>>>> available URI schemes are? >>>>> > >>>>> > Even if this were available via Disco, it would make no difference. >>>>> You couldn't build your app to compensate. I think >>>>> per-implementation/service documentation is sufficient here. >>>>> >>>>> Doesn’t that mean that one can’t implement a Rayo client without >>>>> reference to per-server documentation? >>>>> >>>> >>>> One could certainly implement a client library/framework, and we have >>>> done. When one builds / deploys an application, however, one must know >>>> something about the server implementation. I maintain, though, that Disco >>>> as documentation is no better than normal documentation. I'd love to hear >>>> your argument for Disco being useful here, but it sounds like we're just >>>> trying to tick a "haz Disco" checkbox for no reason. >>>> >>>> >>> >>> I'd expect a generically built client to be possible, and I would expect >>> a baseline that ensured it did the basics if at all possible. >>> >> >> I think the best we could do right now is "must support sip:". But then >> someone will come along and say "what about Jingle?". Then we'll have a >> fight over it where the IVR implementations don't give a crap about Jingle >> and the XSF demands support for it and doesn't care about SIP >> and...deadlock. >> >> > > I've no objection to stipulating a baseline of SIP if that's what the > market needs. > Then I'll do that and pray that your position is representative of the XSF Council. If it's not, then I'd love to hear so soon because that is a fight no-one will win and it'd be better for me to just retract the spec. > If this isn't possible, I'd like to know why not - I've only seen this >>> with Jingle video calling in the past due to the intersection of deployment >>> and patents. >>> >>> I would have thought that some mechanism for discovering what URI >>> schemes were possible would be both possible and useful. >>> >> >> Possible, sure. Useful...for what? >> > > Since otherwise it's not clear when you get a client that it'll work (or > not) with your server. > I still cannot imagine what I, as someone who has built Rayo applications for the last 3 years, would use this for. I'd appreciate someone contributing this part to the spec if they have a use for it. > > > 10) 6.2.1.1 Use of presence for sending of notifications like this >>>>> seems off. I realise this boat may have sailed, but it doesn’t seem right >>>>> to me. >>>>> > > >>>>> > > We had this discussion during the Last Call, and the only >>>>> alternative that was presented was a dependency on PubSub, against which I >>>>> believe I presented a solid argument previously. >>>>> > >>>>> > I’m not exactly ignoring this comment, but I don’t have a sensible >>>>> reply either. >>>>> > >>>>> > > 16) 6.3 The identifier for calls here is always a JID, isn’t it? >>>>> If that’s the case, it’d make more sense to be using JIDs here, instead of >>>>> adding the layer of indirection of a URI with a fixed scheme. >>>>> > > >>>>> > > A call URI will not necessarily always be a JID. It has been the >>>>> intention since the start of this spec to leave open the option of other >>>>> transports for Rayo, such as HTTP. >>>>> > >>>>> > In such a case, how will an entity know about the available schemes, >>>>> and connect to them? If the implication is that there will need to be >>>>> changes later to express how to interoperate with future systems, it >>>>> suggests it wouldn’t be appropriate to push to Draft now with those >>>>> changes >>>>> pending. >>>>> > >>>>> > Any such behaviour is very much a future concern; no-one has given >>>>> it any solid thought yet. Simply remaining generic in using URIs rather >>>>> than protocol-specific addresses seems harmless to me, though. >>>>> >>>>> Possibly harmless, but it’s what it implies that might be troublesome. >>>>> Pushing to Draft now with the expectation that new URI schemes that >>>>> require >>>>> changes to the spec will be produced later wouldn’t be appropriate. >>>>> >>>> >>>> So we just stay Experimental until someone explicitly declares they >>>> will never pursue any changes come what may? >>>> >>>> >>> >>> No, but Draft status implies that at least specific changes are not >>> anticipated, and that any changes are going to be avoided, backwards >>> compatible if at all possible, and are certainly gated through Council >>> approval. >>> >>> So I'd expect here that even if new schemes were able to be added, >>> there'd be a baseline and ideally a discovery mechanism. >>> >>> >>>> > > 17) 6.3 I think here we’re getting into the territory where >>>>> presence stanzas are really not inappropriate for this >>>>> > > >>>>> > > Do you have an alternative suggestion, or a concrete argument >>>>> against? >>>>> > >>>>> > I’d have thought that (for this case) just sending the message >>>>> (probably as headline?) would be more appropriate? This seems to be trying >>>>> to send what is logically a ‘joined’ message to the client, rather than an >>>>> update of presence. Presence is generally the current state of an entity. >>>>> If you use presence for ‘joined’ and you first joined A and then joined B, >>>>> and so the most recent presence you received had ‘joined B’ in it, it >>>>> implies under the usual XMPP semantics that your new presence has replaced >>>>> the old one, and thus you’re no longer joined to A. >>>>> > >>>>> > That's the first practical argument against the use of presence here >>>>> that I've heard so-far; thank you. I'll give it more consideration and >>>>> either propose a modification to the spec or produce a counter-argument. >>>>> > >>>>> > > 23) Example 44: This introduces ‘active speaker detection’, but >>>>> doesn’t explain what this is (or reference an explanation), I think. >>>>> > > >>>>> > > It is what it says on the can, and is a common feature of media >>>>> servers. >>>>> > >>>>> > Alright. I feel a bit uncomfortable introducing terms that I >>>>> wouldn’t expect a typical XEP implementor to understand, but maybe it’s >>>>> alright in this case. >>>>> > >>>>> > I highly doubt a "typical XEP implementor" would be interested in >>>>> implementing a fully compliant Rayo server unless they were also a member >>>>> of the set of people who had heard that term before. See later points for >>>>> more. >>>>> >>>>> Well, rather the point of publishing as XEPs is that other people >>>>> /can/ come along and implement it. Will comment more on later points when >>>>> I >>>>> get to them, I expect. >>>>> >>>>> >>> >>> FWIW, I agree with Ben here. If Active Speaker Detection is a term of >>> art within the field, it seems like prerequisite knowledge. A reference >>> would be nice, but aside from knowing it means detecting which entity on >>> the call is currently speaking, I'm not sure what it would provide. >>> >>> >>>> > > 33) 6.5.4 - How is discovery of the optional/extensible mechanisms >>>>> discovered? >>>>> > > >>>>> > > It's not. Server documentation only. >>>>> > >>>>> > If it’s not discoverable, how would a client written without >>>>> reference to a particular server’s documentation interoperate with it? >>>>> > >>>>> > It would not, and it could not reasonably hope to. I see no benefit >>>>> to discovery here; it wouldn't change the situation any. >>>>> >>>>> I’d like to be sure I understand this, because it seems somewhat >>>>> important. Do you mean that following XEP-0327 is not sufficient to >>>>> implement a Rayo Client (or server)? >>>>> >>>> >>>> Please explain how Disco would make any difference. >>>> >>>> >>> >>> It's not specifically disco, any discovery mechanism would do. >>> >>> If I have implemented a Rayo client, how does it know whether the server >>> it's using will support its required and/or supported mechanisms? >>> >> >> And my counter-point: once it discovered such information, what would the >> client do with it? >> > > We could just pretend that I have a general dislike of things which > *could* be discoverable but aren't. > > But in practical terms, you seem to be insisting that a client is > something written specifically for a particular server. > > In which case what good is it doing to put this specification through the > XSF? > Any client library or framework (see Adhearsion/Punchblock for precedent) would not benefit in and of itself from any such discovery, much the same way a generic XMPP library would not. An application based on those libraries would use certain features of the specifications which impact the choice of server implementations they have. If a specific group chat application was looking for an XMPP server, it would have to (components aside) choose one which implements the server-side parts of MUC) for example. If a MUC-specific client application was used against a server which does not implement MUC, then the best it could hope to do is fail to launch saying "get a better server". Is your point about failing fast vs attempting to process a call and failing mid-way, in a case where one deploys against an insufficient server? Either way, one would get a usable error. > > > 35) 6.5.4.4 - When would the nomatch expect to be triggered? >>>>> Presumably it’s not firing off e.g. whenever anyone says anything that >>>>> isn’t a DMTF when a DMTF input is configured? Can it trigger multiple >>>>> times, or is it removed after a match? >>>>> > > >>>>> > > A nomatch event would trigger in such circumstances that input is >>>>> received which does not match a grammar. Input for a particular modality >>>>> (eg speech or DTMF) is not received by a recognizer unless a grammar is >>>>> specified for that modality. A nomatch is not a standalone Rayo event, but >>>>> delivered as a completion event reason, and as such can only be fired once >>>>> for a given component. >>>>> > > >>>>> > > These semantics are standard for speech recognizers and do not >>>>> warrant specification in Rayo beyond what is already written. >>>>> > >>>>> > I’m not (yet) convinced that that’s true - one should really be able >>>>> to implement a XEP without needing implicit knowledge of how it should be >>>>> implemented. I think I could write a compliant implementation as things >>>>> stand that is very much not what you expect, so tightening this up seems >>>>> sensible to me. Others may disagree. >>>>> > >>>>> > I disagree that one could expect this XEP to contain a recipe for an >>>>> implementation. If it were to attempt to it would run to many volumes. >>>>> This >>>>> specification is not a typical small add-on to an IM scenario. >>>>> > >>>>> > > 36) 6.5.5 - I think the rules for what happens to the output when >>>>> input begins aren’t defined. Although it’s implied that the output stops, >>>>> does it continue again after input? >>>>> > > >>>>> > > No, this is specified as barge in behaviour, which is well >>>>> understood in the field of IVR, and as such does not warrant >>>>> re-specification in Rayo. >>>>> > >>>>> > I think the same holds true here as does for the previous point. >>>>> > >>>>> > The point about "active speaker detection" holds here. If one is not >>>>> familiar with the term "barge in" and what happens in such a scenario as >>>>> is >>>>> widely understood in the field, then one would not be successful in >>>>> building a useful implementation of a Rayo server. >>>>> > >>>>> > At some point the specification of the protocol has to give way to >>>>> what is considered prevailing knowledge, much like MAM does not contain >>>>> details of how to implement a database. >>>>> >>>>> Well, MAM doesn’t detail how to implement a database (and one need not >>>>> use a database to implement MAM), but if there are points where one would >>>>> need to understand how to implement a database in order to implement MAM, >>>>> that seems like a shortcoming in MAM (Although saying that, I think one >>>>> might reasonably argue that ‘a database’ is pretty much universal as a >>>>> concept amongst devs (or, indeed, the general populace), while barge-in in >>>>> this sense is not). >>>>> >>>> >>>> It is universal among people who have an interest in this specification. >>>> >>> >>> Unfortunately it's also a really hard term to find via Google. >>> >>> Maybe a sentence of explanation might help: >>> >>> "Prompt is a convenience component to wrap input and output components, >>> combine their lifecycles, and allow input to barge-in on an output >>> component in the standard sense - that is, it allows additional callers to >>> join an active call uninvited using a special authorization." >>> >> >> Ok, so I see there's some mis-understanding. Barge-in is, in a prompt >> situation, where one interrupts the output by providing early input. Think >> calling Fedex and not wanting to wait to hear the menu before mashing 0 to >> get a human. You just "barged" the output part of the prompt, which >> terminated as soon as you began providing input. >> >> > > OK, so in that case I think you need an explanation in the text, since > that term of art seems to be used in multiple ways in the industry, and > isn't, as you suggested, "universal". > I will add a brief explanation for disambiguation. > > > 41) 6.6.2 - if the client can’t handle the call, what’re the other >>>>> options than rejecting it? (MAY) >>>>> > > >>>>> > > It may simply ignore the offer and allow it to be accepted by >>>>> another PCP. >>>>> > >>>>> > Does that mean that this is effectively “MUST either reject the >>>>> call, or ignore the offer to allow it to be accepted by another PCP”? >>>>> > >>>>> > Sure, but it seems odd to me that we would specify that a client >>>>> MUST not take any action on a received stanza. Is that really >>>>> necessary/desirable? >>>>> >>>>> “MAY reject it, or MAY ignore it” would work fine for me too, without >>>>> a MUST. >>>>> >>>>> >>> I'd personally be more interested in knowing what the semantics of >>> rejection are. >>> >>> Does rejection mean the call request is terminated, whereas ignoring it >>> means the call request continues? >>> >> >> Yes. I'll make a note to flesh this out. >> >> >>> Does the text above Example 84 refer to the call already being accepted >>> by this client, or another? >>> >> >> Examples 83 and 84 are alternative responses to example 82. >> >> >>> > >>>>> > > 42) 6.8.1 - is feature-not-implemented an odd error to use for a >>>>> protocol violation? >>>>> > > >>>>> > > What would be the appropriate error to use here? >>>>> > >>>>> > bad-request is probably closer: >>>>> > >>>>> > "The sender has sent a stanza containing XML that does not conform to >>>>> > the appropriate schema or that cannot be processed (e.g., an IQ >>>>> > stanza that includes an unrecognized value of the 'type' >>>>> attribute, >>>>> > or an element that is qualified by a recognized namespace but that >>>>> > violates the defined syntax for the element); the associated error >>>>> > type SHOULD be "modify”.” >>>>> > >>>>> > whereas feature-not-implemented would be: >>>>> > " The feature represented in the XML stanza is not implemented by the >>>>> > intended recipient or an intermediate server and therefore the >>>>> stanza >>>>> > cannot be processed (e.g., the entity understands the namespace >>>>> but >>>>> > does not recognize the element name); the associated error type >>>>> > SHOULD be "cancel" or "modify”.” >>>>> > >>>>> > This distinction is exactly why I chose feature-not-implemented. An >>>>> "unrecognized value of the type attribute" or other such bad-request would >>>>> look like this: >>>>> > >>>>> > <message type="dog"/> >>>>> > >>>>> > The protocol violation here would be of 6121, which this example >>>>> (6.8.1) does not violate. >>>>> >>>>> 327 says that anything other than ‘normal’ is illegal, doesn’t it? >>>>> It’s that rule that would be violated, making me suggest bad-format. >>>>> >>>>> > Further precedent at >>>>> http://xmpp.org/extensions/xep-0045.html#reservednick and likely >>>>> elsewhere. >>>>> >>>>> I don’t think that’s a similar situation - that’s showing what a >>>>> server that chooses not to implement an optional feature returns if a >>>>> client tries to use it. The case in point here is how the server responds >>>>> to a client sending something that it cannot possibly understand, because >>>>> the protocol isn’t allowed? >>>>> >>>> >>>> No. This is exactly the same situation. This is an optional feature of >>>> the Rayo spec. >>>> >>>> >>> >>> Well, XEP-0327 as written says servers MUST reject the traffic, so >>> clients cannot possibly expect this to succeed. >>> >> >> I don't follow. Where does it say that? >> > > "If a message is directed to the call's JID with a type other than > 'normal' then the server MUST return a <feature-not-implemented/> error" > > That's not optional. > The discussion here is wether sending messages of any type at all is required. It is not required for a Rayo server to implement any message stanza to a call. It is possible to implement messages of type 'normal'. I'm not sure how I can make this any clearer; it makes perfect sense to me and I'm failing to understand why it's not making sense to other people. I'm really sorry, but I think we're at an impasse. I'm convinced that what is written is correct and that the comments against it are a misunderstanding, but I cannot think of a way to say it that removes the misunderstanding. > >> >>> There's no optional behaviour here. As such, this isn't an unimplemented >>> feature, but a bad request. >>> >>> This isn't a hill for me to die on, though. >>> >>> Dave. >>> >> >> >
