Don't get too excited yet, I'm just sharing the plan. The implementation has yet to happen 
First of all, let me provide some context:
Specs is a library implementing the Entity-Component-System pattern. I've been working on it for nearly two years and in the last few months, I've thought a lot about its problems, how to fix them and generally how to improve the whole library. Going into detail about the problems of Specs is out of scope here.
I've decided that it makes a lot more sense to start a new library - nitric - instead of reworking Specs (read below for the exact plan). For one, there are many people currently using Specs and experimenting in the same repo would cause both confusion and a lot of breakage. Secondly, if the experiments fail we still have Specs. And thirdly I want to adjust the scope of the new library.
I think nitric's README explains everything pretty well, so I'm just gonna paste it here:
nitric
General-purpose data processing library.
Status notes: highly experimental, unfinished, work in progress, not recommended for use
This library is meant as a successor for Specs, a parallel ECS library. However, nitric aims to be more general and composable than Specs. In fact, Specs can be implemented as a frontend for nitric once this library is complete.
Motivation
Specs has many problems, both big and small. The library grew big without much planning and as it is now this will continue and make it very hard to maintain. That's what made me think about what I want to create. This is what I ended up with:
Vision
The vision for nitric is to provide a set of crates that evolve as the standard way to solve data processing problems. There were already very interesting use cases for Specs, including using it for a compiler and performing larger simulations, both outside of Specs' original scope (ECS for game development). This is what I intend to make nitric suitable for. So to list a few examples of what nitric could be used for in the future:
- game development
- game physics
- simulations
- compilers
- data validation
- Graphical User Interfaces
The question of how to structure your library/application is a very common one, everywhere in programming. The plan for nitric is not to force any of them, but to provide useful and modular facilities that allow for specific patterns (e.g. Entity Component System (1)), and to provide "recipes", similar to the Rust cookbook that show how common tasks can be solved. Nice side effects of that are that we can work on one implementation, that is efficient and can allow for neat extra functionality (debugging facilities, profiling, easy multi-threading, etc.).
(1) for ECS, also see this great presentation by Catherine West
Philosophy
nitric will be a collection of crates all about processing data. All of its crates follow this philosophy:
- Only solve a single problem, in a reasonably composable way
- Expose a general, composable and robust API
- APIs should either be designed to not produce any error cases or return a
Resultwith only the possible error conditions - Do not assume how the API is being used (-> composability)
- Expose internals in a
*-internalscrate for stability by default, with the option to opt into more unstable facilities
- APIs should either be designed to not produce any error cases or return a
- Impose minimal friction to use
nitric
Using nitric as ECS
How will this allow you to use nitric instead of Specs? Here's the tentative design for ECS:
nitric-entity: Provides entity allocators, storages, and with that mappings between entities and components
This would already be enough to have an ECS. Systems can simply be functions that accept references to the storages and eventually the allocator. In fact, that is the recommended way for libraries to expose their API; libraries should not assume how the code is executed. For example:
(pseudo code for now)
pub fn process_local_transforms(
local: &Storage<LocalTransform>,
global: &mut Storage<GlobalTransform>,
parents: &Storage<Parent>)
{
// compute global transforms
}
If those component storages come from a dynamically typed, string mapped HashMap, fine. If they are stored in a struct - works, too. How systems are run also doesn't matter.
Now, there surely are other things Specs users would miss, so the next crate will be...
nitric-world
As you might have guessed, this provides a map that can store arbitrary component storages. In contrast to Specs, I also plan to include support for multiple values of the same type by allowing an additional key (e.g. a string).
nitric-graph
This will be a re-worked version of shred's Dispatcher, allowing to parallelize data processing (execution of systems). A "system" will simply be a FnMut(T) -> R, which means it's up to the user how the data is fetched (nitric will provide solutions for this, but it doesn't force you to use any of them).
Structure
The main crate, nitric will simply serve as a top-level crate for re-exporting all nitric-* crates. However, since everything is optional, nitric is controlled with Cargo features, only exporting the crates for which you enable the flag.
FAQ
What does this mean for Specs?
For the immediate future, this has no effect on Specs. It will not be deprecated. The biggest change for now is that I won't spend much time on it (just merge PRs and fix critical bugs).
As for when nitric is in a usable state, that has yet to be seen. In any case, it should be possible to make Specs a thin wrapper over nitric crates (if that's necessary). All that depends on how well nitric will be adopted.
What does this mean for Amethyst?
Amethyst (a game engine that makes heavy use of Specs) will continue to use Specs. Whether it will use nitric in the future will be decided by all members, through the usual RFC process.
That's the plan so far! If you're interested, feel free to check out the repository:
Also, I'd love to hear about your thoughts & additional requirements. I've started writing up the requirements here, but the list is far from complete.
Lastly, I want to say thank you.
Thank you to @kvark and @csherrat for starting Specs in April 2016 and building the foundation of it.
Thank you to all the people who contributed ideas and code to Specs.
Thank you for all the feedback on Specs which gave me the courage to further work on it.
The project wouldn't exist like this without you.
