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. > > > > 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. > > > 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? > > > 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. > > > > 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. > > > 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. > > > 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. > > > > > > 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. > /K > >
