Re: [vwrap] Comments on http://tools.ietf.org/html/draft-ietf-vwrap-intro-00

[Morgaine <[e-mail]>]

Welcome Cristina to the working group!  And without further ado, let me say
that you are spot on.

I had made it known previously that I was trying to rewrite the intro
document.  Those who have followed my specific areas of interest throughout
the 3-year process of AWG/OGP/MMOX/OGPX/VWRAP will have known what to
expect:  a complete dismissal of any attempt to create a single world, a
focus on interop between multiple worlds, separation of world policies, and
a specific use case that embodies all of these:  the direct support for
tourism between virtual worlds.

David spoke to me yesterday to find out how my document editing work was
going, and I admitted to him that I was somewhere between desperation and
failure.  I had started off making relatively small changes to eradicate
"single world" thinking from the document, but after some pages' worth of
such changes, I realized that this was applying band aids to cure a broken
leg.  The document is simply wrong in its entire approach.  I asked for
David's advice and offered to explain the problem I saw to the group this
weekend, at which point I noticed Crista's post.

I believe that you are 100% right in your observations, Crista.  The intro
document is way off base as an introduction to the work of a group whose
fundamental purpose is to provide protocol standards for VW interop.  It
doesn't even mention interop between VWs at all!  It's hard to imagine how
it could be further from the intended goal.

This problem is with us because it all started with *OGP*, a product of a
single-minded desire to grow Second Life by adding individual or multiple
regions to the existing SL world (or similar walled garden worlds), without
any policy rights of their own and without interoperability between such
worlds.  I'm not guessing about this.  I've been with the process from the
start, and attempts to discuss asset sharing for VW interop were rejected in
OGP.  In the last half year we have at least managed to put multi-world
deployments on the agenda through the help of David's "deployment patterns",
but nowhere is this reflected in the existing protocol documentation.  The
core (legacy) documents which originated with OGP do not reflect our goals,
at all.

A few words on the scope of our "VWRAP deployments".  These are expected to
cover the entire gamut from individual walled garden worlds through to a
metaverse full of interoperating but otherwise independent virtual worlds.
Clusters of access-controlled worlds of various kinds would fall somewhere
in the middle, perhaps the VW counterparts of business VPNs.  Because of the
OGP legacy, we have been unable to document anything but the closed worlds
part of this spectrum.  We haven't even established a vocabulary for
examining the key process of VW interop, which is the shared access to
assets that gives rise to the visual client-side mashup which is the end
product of all this.

I've tried on numerous occasions to bring our discussions to focus on the
worlds tourist use case, because this is the one that highlights the areas
of difficulty.  Restricting a full-interop protocol to create walled gardens
is easy, whereas expanding a protocol for walled gardens into one that
handles VW interoperation is not, so we need to focus on the larger issue
first and only create mechanisms for restriction in passing.  Just in case
this point isn't clear, we should note that even in the most tightly
controlled networks (such as military ones), there is always a need to
interoperate with the world outside.  Thinking about only the closed system
as your primary requirement just gets you in trouble later.

Thank you Crista for describing in detail the "impedance mismatch" between
our documents and OpenSimulator's model or goals.  Since OpenSimulator (or
more accurately the worlds that use it) provides our primary example of
worlds for which VWRAP would be expected to be relevant, your observations
are more than just accurate and devastating --- they are also the key to
getting us to where we want to go, if VW interop is our goal.  It certainly
is mine.

I recommend that we start from scratch on an entirely new intro document, in
which we establish first, very explicitly, that our problem domain is that
of multiple virtual worlds and interoperation between them.  We tried to
approach this in the past, but all attempts were blocked by the incongruous
proposition that "we don't know what virtual worlds are", which verges on
comedy.  More importantly however, as Crista has pointed out, it should be
none of our business "what virtual worlds are" --- all we need to discuss is
how they can interoperate.  After all, SMTP doesn't need to know how MTAs or
MUAs are structured, all that matters is how they communicate, and the same
is true here.

Crista, while our current IETF drafts seem not to address the main issue at
all, you may find that the following article is more closely aligned with
what I believe is our intended direction, written by Joshua, David and
myself for IEEE Internet Computing, published in February.  The article is
embarrassingly over-optimistic in suggesting that the OGP model leads
towards VW tourism despite no such operation having been designed, but at
least it expresses the intent.  We need to go beyond intent though.
http://internetmessagingtechnology.org/pubs/VWRAP-for-Virtual-Worlds-Interoperability-mic2010010073.pdf

Thank you very much for your effective post.  I think we should use it as a
catalyst for affirming our interop direction to be between multiple
independent worlds, and actually getting ourselves on the right road to
achieve it.


Morgaine.





====================================

On Tue, Sep 7, 2010 at 4:56 PM, Cristina Videira Lopes <[e-mail]>wrote;wrote:

> This is my first time participating in an IETF WG, so apologies in advance
> for any mis-steps on the process. I believe it's ok to send comments at this
> point. But I understand that the work has been going on for about a year
> without me being involved, so my comments may be out of order. This is one
> year's worth of comments, long and heavy email :-)
> I leave to the Chairs of this WG the right to dismiss them, and I'll accept
> it if that happens.
>
> I'm still not entirely sure the world is ready for "standards" for virtual
> world interoperability, but given that this working group exists, I hope my
> comments help strengthen the technical aspects of the work that has been
> going on here, so that, in the end, this document will appeal to others who
> have absolutely nothing to do with the Linden Lab family of virtual worlds
> -- so as to make good on the word "interoperability."
>
> The document seems to be establishing the underlying assumptions and scope
> for the protocols recommended by this group. That's great.
>
> The gist of my comments is that the particular assumptions established by
> the document do not accurately reflect the underlying assumptions and goals
> of the OpenSimulator platform in important ways, and I suspect they also
> don't reflect many other VW platforms. I don't know if that is a good thing
> or a bad thing or an irrelevant thing for the purposes of this working
> group; I'm just making this observation. Assuming that the Chairs accept my
> commentary for discussion, I delegate to the group the judgment on the
> consequences of this observation.
>
> Let me expand on it by going through the document, and pointing out the
> differences in assumptions and goals, as well as the parts of the text that
> aren't clear to me, the parts that I think are good, and some general
> technical commentary.
>
> ----- Comment 1 -----
> Section 1: "...This document introduces the
>  Virtual World Region Agent Protocol (VWRAP) suite.  This protocol
>  suite is intended to carry information about a virtual world: its
>  shape, its residents and objects existing within it.  VWRAP's goal is
>  to define an extensible set of messages for carrying state and state
>  change information between hosts participating in the simulation of
>  the virtual world."
>
> This starting statement offers the concept of a single virtual world;
> reading further  it seems to mean that the ecosystem of VWRAP is, indeed,
> treated here as one single system involving a multitude of organizations.
> Section 2.1, par 5:
> "The VWRAP suite assumes network hosts, likely operated by distinct
>  organizations will collaborate to simulate the virtual world."
>
> The OpenSimulator platform has been designed with a plurality of virtual
> worlds in mind, not just one. This plurality is a fundamental assumption of
> our platform, as it makes aggressive use of plugins for two important
> aspects of virtual worlds: (1) the scene server -- scene renderer client
> interaction; (2) the scene service -- resource services interaction.
>
> What the use of these plugins means is that we strongly believe that each
> virtual world is an independent system that should be designed and
> implemented in a way that best fits that world's goals. We believe this for
> OpenSimulator-based worlds already by providing those important aspects as
> plugins, so we also believe it for virtual worlds that aren't based in
> OpenSimulator software. The decisions made by, say, Blue Mars, with respect
> to how to send scenes to client software and how to manage their resources,
> are to be respected and treated independently of the decisions made by, say,
> ReactionGrid. But that doesn't mean that worlds operated by these
> organizations can't interoperate. They can, given a minimum interoperability
> protocol. In summary, and this will recur throughout my commentary:
>
> OpenSimulator does not assume the existence of one single virtual world
> involving a multitude of organizations; it assumes the existence of multiple
> virtual worlds, each one under the authority of one single organization --
> which, in turn, may make its own internal decisions about sharing ownership
> and resources of parts of that world with other organizations, but that is
> an internal decision that is irrelevant for purposes of virtual world
> interoperability.
> For some background on the virtual world model assumed by OpenSimulator,
> see
> http://opensimulator.org/wiki/Virtual_World_Model
>
> ----- Comment 2 -----
> Section 2.1, the list of 3 characteristics:
>
> "1. The virtual world exists independent of the participating
>  clients." ... "VWRAP assumes the state virtual world is "always on"... "
>
> OpenSimulator does not make these assumptions. While OpenSimulator worlds
> are usually run on servers to which clients connect over the network, it is
> possible to take the OpenSimulator framework and merge it with a renderer
> component, producing a virtual world that is both a client and, eventually,
> a server if that virtual world is to support multiple users over a network.
>
> Also, OpenSimulator does not assume that the virtual world is "always on",
> on the contrary. Many OpenSimulator-based virtual worlds that already exist
> seem to be ran on people's personal computers in their home networks, which
> are often turned off.
>
> "2. Avatars have a single, unique presence in the virtual world."
>
> OpenSimulator does not make this assumption. It is possible to have
> multiple presences (sessions) for the same user on the same virtual world.
> This supports use cases of users wanting to be in two different places of
> the world at the same time, e.g. for attending two different events. The
> decision on whether to allow this or not pertains entirely to the virtual
> world operator.
>
> ----- Comment 3 -----
> Section 2.2, architectural patterns:
>
> "1. Systems implementing virtual world services must be distributed."
> ...
> "But however large (or small) a virtual world deployment is, or
>      how many distinct organizations contribute to its operation,
>      software implementing virtual world services MUST assume
>      resources required to perform its function are distributed
>      amongst multiple hosts."
>
> OpenSimulator does not impose this. In fact, the most popular configuration
> of OpenSimulator-based worlds is a "standalone" configuration where both the
> scene service and all the resource services of that world execute in one
> single process of one machine. In a standalone VW system, none of the
> services (e.g. assets, inventory, etc) are "distributed." Furthermore, as
> explained above, the OpenSimulator framework also supports the existence of
> single-process virtual worlds that include the renderer itself.
>
> The only two requirements imposed by OpenSimulator, and indeed by any
> software system, are: (1) in cases where these worlds wish to serve multiple
> users over the network, then network endpoints must exist that serve the
> scene to the clients used by those users; (2) in cases where these worlds
> wish to interoperate, then network endpoints must exist that serve certain
> resources from those worlds to other worlds.
>
> "2. Services supporting collaboration are hosted on 'central'
>  systems."
>
> No such assumption in OpenSimulator. The way that virtual world operators
> decide to design and implement their collaborative features are entirely up
> to them.
>
> For example, in OpenSimulator the default implementation of Instant
> Messaging is peer-to-peer, with only presence being looked up centrally;
> there is no central IM server. This feature is implemented as a plugin, so
> other implementations (e.g. centralized) are possible.
>
> Maybe this architectural pattern pertains to inter-world collaboration? If
> that is the case, then this is clearly not a desired goal, as most
> OpenSimulator virtual worlds want to operate their own collaboration
> sub-systems, and do not wish to depend on third parties, unless there is no
> alternative. As an example, take the Groups service, which is implemented
> outside of the OpenSimulator core distribution. While there is an instance
> of that group service ran by an individual (the original developer) that can
> support groups for many virtual worlds, most grid operators choose to run
> their own instance.
>
> "3. Virtual world services default to being 'open'."
> ...
> "In other words, requiring
>      two services (e.g. - physics simulation and asset storage) be
>      managed by the same organization's servers is an issue of local
>      policy, not of protocol."
>
> I don't understand what 'open' means. Does it mean that they default to
> being available on the internet? The quoted sentence doesn't seem to relate
> to the headline, so I'm not sure what this architectural pattern is saying,
> I think it needs to find its message.
>
> ----- Comment 4 -----
> Section 3.1:
>
> This is the best section of the document, but it needs a lot more depth. I
> would go as far as suggesting that protocol flexibility (and not just data
> presentation flexibility) may very well be the single most important
> contribution that an interoperability standard in this area might make.
>
> Indeed, this document fails to address one critical question: what
> assumptions do we make wrt how the server serves scenes to the clients? Do
> we assume that this is a fixed part for interoperability (i.e. there's only
> one protocol for doing this in the entire collection of interoperable
> virtual worlds) or so we assume that each virtual world does it in whichever
> way it wants?
>
> To illustrate the issue, let me point out the spectrum of possibilities.
>
> On one extreme we have what is currently emerging on the Web: on-line,
> multi-user 3D scene servers that simply send their "viewer code" to the web
> browsers in JavaScript. You go from one game to another, and you get
> radically different pieces of JavaScript code that get the data from the
> servers and render it; these JavaScript "viewers" are black boxes that have
> nothing to do with each other.
>
> On the other extreme of this spectrum, we have systems like Second Life and
> World of Warcraft, with customized, non-programmable viewers that do things
> in exactly one way, tightly coupling the protocol with the fixed
> game-specific UI.
>
> Somewhere in the middle, we have Flash-based worlds (and others) that run
> on the general-purpose Web browser and that are identified by certain MIME
> types (e.g. application/x-shockwave-flash).
>
> So where does this group stand wrt this critical issue?
>
> As I said above, in principle, OpenSimulator assumes that each virtual
> world has its own client-server protocol -- so in line with what is emerging
> on the Web. Unfortunately we still don't have viewers capable of doing this
> well: Web browsers still can't render the kinds of content we need, and
> existing VW clients aren't general enough. But that should not be an
> impediment to accepting the underlying principle of letting VW systems do it
> their way, and having that be a programmable component of a possible
> interoperability framework.
>
> With this, we set up an interoperabilty framework that accommodates the
> variety of protocols that already exist, and that are unlikely to be let go
> by their implementers. We also set up the stage for accommodating the
> variety of protocols that still don't exist but that are bound to happen as
> the Web starts experimenting with 3D immersion.
>
> ----- Comment 5 -----
> Section 3.2:
>
> This section expands more on the basic VWRAP premise of "the single virtual
> world" composed of multiple services under the authority of multiple
> organizations. As explained before, this is very different from the VW model
> assumed by OpenSimulator, where a myriad of virtual worlds, each under one
> authority, are assumed to exist, and where the internals of those virtual
> worlds are out of scope.
>
> ----- Comment 6 -----
> Section 3.3:
>
> This section is contrary to the design philosophy of OpenSimulator, where
> very few conditions are imposed on the internal implementation of virtual
> worlds.
>
> ----- Comment 7 -----
> Section 4.1:
>
> This section seems to be a summary of the document
> http://tools.ietf.org/html/draft-ietf-vwrap-authentication-00
>
> That document seems to describe a straightforward login procedure, similar
> to all login procedures out there that authenticate a user onto a service
> running on a server. It defines specific on-the-wire data representations,
> and a specific protocol for error handling.
>
> I understand that the introduction of the seed CAP, and subsequent
> invocation, is a new thing that most login procedures don't have.
>
> But I'm at loss as to why this matters for interoperability purposes. Each
> virtual world should be free to do the initial user authentication in
> whichever way it finds most suitable, and to send whichever information it
> needs to send, in whichever way, to the client.
>
> Maybe CAPs has a special role in inter-world authentication in VWRAP?
> Unfortunately, I read all the available documents, and I couldn't find
> anything that explains inter-world authentication in VWRAP.
>
> ----- Comment 8 -----
> Section 4.2:
>
> This section introduces concepts that haven't been explained before and
> that aren't explained here either, specifically "agent domain" and "region
> domain". I know what these are, as I've read the AWG documents on the Web;
> but another  less informed reader won't know.
>
> Many other things in this section are unclear because of the non-existence
> of referenced materials e.g. "VWRAP Teleport specification", so perhaps
> these summaries shouldn't be in this intro document at all. But since they
> are, let me offer some comments.
>
> In 4.2.2: unclear, but I'm assuming this section pertains to inter-world
> movements? That should be made clear. Because intra-world movements should
> be out of scope for interoperability purposes: the way that virtual worlds
> choose to move the agents within themselves, if they do at all, is
> irrelevant.
>
> I believe there is some confusion here between model and mechanism, but
> maybe I know too much. I'm assuming that the word "capability" in VWRAP
> means "capability URL"; if I'm wrong, and if it means just "capability" as
> given by the Webster dictionary (roughly, authorization), then that would be
> great!
>
> Also in 4.2.2 there is an underlying assumption that the client keeps a
> direct connection to the "agent domain". For example "The client signals to
> the agent domain its desire to move..."
> The standard Linden client does not do this. But more important than the
> Linden client, Web browsers, i.e. stateless clients, also don't keep state.
> So if we ever were to have a Web-browser-based viewer for a web of virtual
> worlds, we wouldn't be able to do what is suggested in this entire section.
>
> These protocols hinted at in this section are the crux of interoperability.
> I understand this is just the intro document, and it's not supposed to have
> all the details, that's fine. If you go ahead with the protocol hinted at
> here, then it is important to note somewhere in this intro document that it
> assumes stateful clients, and that Web browser viewers (that aren't browser
> plugins) are N/A.
>
> As I said in comment #4, I would like to see a better analysis of what
> virtual world inteoperability demands from the viewer software. I used to
> think that web browsers were an evolutionary dead-end, but with the
> introduction of HTML5 and all the exciting work that is going on with
> running verifiably-secure native code on Web browsers, I came to change my
> mind about this. Since the Web browser is the ubiquitous client software, it
> seems like a bad move to exclude this client from interoperability for
> virtual worlds, because we're only going to see more 3D immersion, not less,
> on web browsers.
>
> ----- Comment 9 -----
> Section 4.3:
>
> This has nothing to do with interoperability and seems to be focusing
> exclusively on how the Linden Lab world works. Statements like "The host
>  in the region domain responsible for managing spatial chat applies a
>  proximity algorithm to the chat to determine which avatars or objects
>  are close enough to hear it."
> are too specific to be worth mentioning in this document. Other virtual
> worlds may apply different schemes wrt chat.
>
> ----- Comment 10 -----
> Section 4.4:
>
> I suggest replacing the ad-hoc terminology "at rest" and "in world" with
> more standard terminology. Assets are stored in persistent storage. There's
> technical terminology for "in world":  assets that are referenced by a 3D
> scene. There's also technical terminology for "at rest": assets that are not
> referenced by a 3D scene directly but that are referenced by other resources
> like a user's inventory or scripts.
>
> This section is full of details that should not be here:
> (1) how the scene server decides to manage the assets is an internal
> decision of each virtual world. The scene server may have its own assets, or
> it may have its own asset storage server on the same data center, or it may
> use amazon. It may pre-fetch or may perform lazy fetch. It may cache or it
> may not. It doesn't matter for the purposes of interoperability.
> (2) how the scene server decides to make the assets available to the
> clients is an internal decision of each virtual world; in fact, a central
> part of the client(viewer)-server protocol, of which there should be many.
> It may send them on-line via UDP; it may zip them up in a zip file and send
> them; it may tell the client to fetch them from another server. It doesn't
> matter.
>
> Interoperability should not impose any conditions whatsoever on how these
> things are done, or the word "interoperability" will start moving into the
> realm of internal virtual world architecture, which is something this group
> probably should not be doing, lest alienating potential parties. Even in the
> small ecosystem of OpenSimulator, we are already seeing a variety of new
> clients being developed that have nothing to do with the Linden Lab client
> (e.g. Unity3D). That's a direction that we very much encourage.
>
> ----- Comment 11 -----
> Section 4.2.2:
>
> This section seems to be implying that host based trust carried by X.509 /
> PKIX certificates will ensure that the receiving party will honor the
> asset's metadata. These (i.e. certificates and honoring the metadata) are
> two different things. It should be made clear that, just because all parties
> are who they say they are, it doesn't mean that they will honor the
> metadata.
>
> Again, I wish I knew more of what people in this group have in mind for
> authentication, but I couldn't find any information.
>
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