Thanks for this - it is a helpful clarification. I rarely mean
criticism in a personal way so appreciate the background.
I have looked at the work involved and there is quite a lot. I
appreciate where Mic is coming from as I have the same dilemma ( with
even fewer resources than Intel!).
On 6 Jan 2010, at 16:10, [email protected] wrote:
Tom Willans wrote:
Are some aspects of the interface more settled than others? I
appreciate
that this is a judgement call.
Yes, some aspects are more settled than others.
First, let me point out where this comes from, so that you and others
can understand better.
Up to recently, there was no such thing as
OpenSim.Services.Interfaces,
nor the companions OpenSim.Services.Connectors and
OpenSim.Server.Handlers. The interaction between the simulator and the
resource services, and among the resource services themselves, was a
mess. I don't mean it in a criticizing attitude, early-stage code is
usually a mess. The broad stokes were there, and were really good, but
the details were a complete mess. Simple questions like "what handlers
are there?" or "what are the resource service interfaces?" were a
challenge to answer, interfaces and handlers were spread all over the
code, special cases were pervasive, classes were being used directly
instead of interfaces, etc. The user services, in particular, were a
nightmare, with duplication running rampant because of "standalone vs
grid mode", and the code being on the verge of bipolar disorder.
Users,
agents and avatars were being used interchangeably, with no conceptual
distinction, misnomers everywhere, etc.
This refactoring's main goal is to depart from that chaotic mess and
to
instill order in the code base. It is primarily a *refactoring*,
meaning
that code has moved from one namespace to another, but it is also a
rewrite -- because in the process of revisiting the code it was clear
that things should be done better than they were being done. In
particular, harmful hard-coded instantiations of classes were replaced
by dynamic loading and instantiation. The core of this is
OpenSim.Server.Base.Utils.LoadPlugin -- this is the core of the ROBUST
model.
Having said that, let me now explain how people who plan to extend
OpenSim should be looking at it.
The main "contract" between the core code and developers of resource
services is the collection of interfaces in
OpenSim.Services.Interfaces.
This is what the simulators call, can't get around hard-coded calls to
those interfaces. Those interfaces will stabilize very quickly. Most
of
them are stable already, with the notable exception of
IInventoryService
which still needs love. But all others will be stable at 0.7. Now is
the
right time for people to look at those interfaces and send feedback
about which things you think are missing.
The next level of reuse is the code in OpenSim.Services.Connectors and
OpenSim.Server.Handlers. This code is less important than the
interfaces, because it's invisible to the simulators, therefore ppl
should be more careful about relying on it. This is quite an important
point that I don't think many people grasp yet, so let me explain.
In most systems, the network protocols are fixed. People go to great
lengths discussing them ad-nauseum in meetings and committees, to
settle
on the right data formats, the right data, etc. NOT HERE. The network
protocols in OpenSim are now dynamically loaded, and therefore
replaceable. There is no such thing as *the* network protocol between
the simulator and, say, the asset server. There can be many -- you can
roll your own. There are reference implementations in the core
distribution, but that's exactly what they are: reference
implementations, they are not fixed protocols. As such, people
should be
careful about relying on those reference implementations.
So, to sum it up: the main contract is OpenSim.Services.Interfaces and
those are going to be stable very soon. The level right under it,
OpenSim.Server.Handlers and OpenSim.Services.Connectors can also be
relied upon but it's less stable. I'm still not happy with many of
those, so they will change after 0.7. People who don't want to put up
with these changes may want to roll their own network protocols.
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