Re: [ogpx] Limits to interoperability of scripted objects

[Joshua Bell <josh at lindenlab.com>]

Good analysis as usual, Morgaine!

On Mon, Oct 26, 2009 at 10:15 PM, Morgaine <morgaine.dinova at googlemail.com> 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.