Re: [ogpx] Limits to interoperability of scripted objects

[Lawson English <[e-mail]>]

Morgaine has seen me hype this many types, but perhaps Joshua and others 
have not not:

http://wiki.secondlife.com/wiki/User:Saijanai_Kuhn/Plugins_discussion ...


There's many uses for client-side scripting, from custom GUIs to 
manipulation of elements (avatars, objects, etc) going out to the sim 
directly, to manipulating objects client-side only say for use in a 
mechanima play where only the other characters in the play can see what 
is going on. Hybrid situations, as is done with the puppeteering code 
mentioned at the bottom of the page, could delay updating until 
everything is resolved client-side. A collection of avatars could be 
participating in a private play, battle, simulation, whatever, and only 
use the main simulator to provide a backdrop for whatever it is they are 
doing with or without eventually updating the simulator as to their 
position/actions/etc.

And no doubt there are many other scenarios that we haven't conceived of 
yet where "client side scripting" would be useful. And one extreme is 
the Second Life use-case where the server handles virtually every aspect 
of the avatar except limited user input. At the other end is the 
Croquet/Cobalt case where clients act as servers for their own private 
worlds that are, in principle, P2P in nature. While the VWRAP scenario 
assumes more Second Life-ish scenarios, there's plenty of room for more 
Croquet-like situations,  IMHO. The server(s) need not know what input 
the client is working with. Perhaps there's enhanced physics being used 
in a special MC Escher style world. or perhaps the client is getting a 
direct feed of planetarium data to light up the sky. Both situations 
exist or are being worked on in a rudimentary way in Second Life itself. 
There's no reason to assume ANY limitations save those required for 
security/trust issues, and those will need to be applied on the server 
side for any realistically secure scenario (assuming that the 
client-side plug-ins are trustworthy for the end-user's purposes, of course)

 
Lawson



Morgaine wrote:
> On Tue, Oct 27, 2009 at 4:51 PM, Joshua Bell <[e-mail] 
> <mailto:[e-mail]>> wrote:
>
>
>     * Your (3) (common scripting environment) is intriguing. Sun's
>     Project Wonderland uses Java (obviously...) as the common format,
>     and (vastly simplifying) all objects in the VW are Java objects.
>     I'd love to learn more from them about the challenges and
>     successes. That said, at a protocol level, I don't think we'd ever
>     dictate a common environment, so going down this road might turn
>     into a de-facto common case of the content negotiation (just as
>     the Web technically allows for client-side scripting languages
>     other than Javascript, although they are used incredibly
>     infrequently in practice). 
>
>     * Client-side scripts are also intriguing. If I think about what
>     this means in practice, it's that the client is able to manipulate
>     the state of objects in-world. Well, duh - that's what editing and
>     appearance tools do! So... that capability (pun intended!) is a
>     requirement at the protocol level, although I don't think we've
>     even brushed on how to define it yet. It would be intriguing if
>     the protocol were such that the client could expose a DOM-like
>     view of the world to local scripts to observe and mutate.
>
>
>  I like both of those ideas.  I wonder if we could support them both 
> in principle with minimal effort by providing a generic hook using 
> script metadata.  Let some attribute select between "region" (for 
> scripts running in the current region as in SL), "avatar" (for HUD 
> scripts that run in-world but don't need region events so they can be 
> run in a separate load-balaced server pool), "home" (for scripts that 
> always run in the agent's home region), and "client" (for client-side 
> scripts or plugins).  Further attributes could specify the language 
> and maybe a startup argument list too.  (These are just random ideas, 
> not cohesive.)
>
> Thinking about the scripting languages themselves, presumably nobody 
> would argue in favour of turning LSL into an interop standard given 
> the poverty of its syntax, but even worse is the tortuous and complex 
> semantic of its system calls which would be very problematic to 
> standardize, or maybe impossible.  The SL scripting environment has 
> evolved in a way that isn't conducive to portability, not only because 
> the implementation is closed and quite unique, but also because it's 
> tied fairly strongly to a proprietary physics engine for 
> events/simulation and to a rather esoteric communications model.  
> These things conspire to make standardising around the SL scripting 
> mechanism very unlikely.  This gives us a solution to cross off the 
> list, but unfortunately doesn't offer us anything in its place.
>
> Being realistic, forcing language commonality at this early stage is 
> just not going to happen, so we might as well lubricate the protocol 
> machinery to allow multiple scripting systems to be supported.  
> Eventually a de-facto standard will emerge as happened with 
> Javascript.  Let people with more spare time than we have sort it out, 
> and may the best idea win. :-)
>
> As lubrication, I think we should provide at the very least some 
> generic and extensible metadata hooks in the protocol for this, 
> otherwise the spec will be modified incompatibly outside of the 
> standard to support the diverse scripting requirements of worlds, and 
> then interop suffers.
>
>
> Morgaine.
>
>
>
>
>
> =========================================
>
> On Tue, Oct 27, 2009 at 4:51 PM, Joshua Bell <[e-mail] 
> <mailto:[e-mail]>> wrote:
>
>     Good analysis as usual, Morgaine!
>
>
>     On Mon, Oct 26, 2009 at 10:15 PM, Morgaine
>     <[e-mail]
>     <mailto:[e-mail]>> wrote:
>
>         Being pragmatic about the situation, if we wish to see interop
>         of scripting in the relatively near future, we need to find an
>         approach that is inherently interoperable.  Here are some
>         ideas that might be relevant to this end (these are
>         alternatives, they don't all apply simultaneously):
>
>            1. Make script state transfer a deployment option:  both
>               source and destination regions have to allow script
>               state transfer for it to happen.
>            2. Worlds running different scripting engine
>               implementations do not transfer state and hence scripts
>               are initialized on teleport.
>            3. Define a common scripting language and virtual machine
>               environment --- ie. a web-like Javascript approach but
>               for regions.
>            4. If script state continuity is desired on teleports
>               between worlds running different script engines, let
>               such scripts run client-side.
>
>
>     A few thoughts on the above:
>
>     * Even though the Web appears to have given up on content
>     negotiation over HTTP, I'm still a fan and I think cross-system
>     interop like this is a good place for it. During Region-to-Region
>     state transfer, you could imagine the destination region
>     advertising the script state types it accepts
>     (vendor/com.lindenlab.secondlife.lsl2mono,
>     vendor/org.opensim.dotnetengine, ...), and the source region
>     delivering one tagged with appropriate type. I would imagine we'll
>     need similar logic for static content as well - articles of
>     clothing could have have "prim" or "mesh" based versions, and
>     regions may prefer one type to another. (Although it would be more
>     likely to have both available on the region, and have content
>     negotiation occur on the region->viewer resource transfer.)
>
>     * Given the desire for "tourist" models (using the term loosely -
>     I "live" on my home grid, but like to visit other grids), it
>     doesn't seem like there's a one-size-fits-all approach (since
>     region-to-region teleports in my home grid and region-to-region
>     teleports between grids utilize the same protocol). So... this is
>     definitely part of the protocol's mandate to sort out.
>
>     * Combining the above two points, it implies that attachments will
>     have to cope with moving from areas where they have scripts
>     running to scripts not running (if the code/state is not
>     compatible with the hosting region). Fortunately, we have
>     precedent for that. :)
>
>     * Infinity and I very briefly hand-waved about whether "portable"
>     content (primarily, attachments to avatars) should even be
>     executed within the region domain. Perhaps they should be
>     executing in the agent domain? That's a radical departure from how
>     SL or OpenSim work today. (If you squint your eyes and partition
>     the current services, at least.) - at any rate, today there is no
>     script execution outside of a region. It's an intriguing idea, but
>     by no means complete - how such fine grained state might be
>     updated between domains, for example. Vehicles come to mind as
>     another case, and those have no clear "home base" for script
>     execution. I suspect this is not tractable for the first iteration
>     of VWRAP, but I don't want to dismiss it.
>
>     * Your (3) (common scripting environment) is intriguing. Sun's
>     Project Wonderland uses Java (obviously...) as the common format,
>     and (vastly simplifying) all objects in the VW are Java objects.
>     I'd love to learn more from them about the challenges and
>     successes. That said, at a protocol level, I don't think we'd ever
>     dictate a common environment, so going down this road might turn
>     into a de-facto common case of the content negotiation (just as
>     the Web technically allows for client-side scripting languages
>     other than Javascript, although they are used incredibly
>     infrequently in practice). 
>
>     * Client-side scripts are also intriguing. If I think about what
>     this means in practice, it's that the client is able to manipulate
>     the state of objects in-world. Well, duh - that's what editing and
>     appearance tools do! So... that capability (pun intended!) is a
>     requirement at the protocol level, although I don't think we've
>     even brushed on how to define it yet. It would be intriguing if
>     the protocol were such that the client could expose a DOM-like
>     view of the world to local scripts to observe and mutate.
>
>
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