[RFC] Event Chaining as a Decoupling Method

rfcs/0002-event_chain.md

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+# Table of Contents
+
+- [Motivation]
+- [Guide Level Explanation](#guide-level-explanation)
+- [Reference Level Explanation](#reference-level-explanation)
+- [Drawbacks]
+- [Rationale and Alternatives](#rationale-and-alternatives)
+- [Prior Art](#prior-art)
+- [Unresolved Questions](#unresolved-questions)
+
+# Basic Info
+[basic]: #basic-info
+
+- Feature Name: event_chaining
+- Start Date: 2020-04-30
+- RFC PR: (leave this empty until a PR is opened)
+
+# Summary
+[summary]: #summary
+
+How we can use event chaining as a way to decouple our different
+modules and Systems.
+
+# Motivation
+[motivation]: #motivation
+
+- Reduced coupling
+- More configurability
+- Better separation of concerns
+- More!
+
+# Guide-Level Explanation
+[guide-level-explanation]: #guide-level-explanation
+<details>
+
+[Link to paper](https://www.jojolepro.com/event_chaining.pdf)
+
+</details>
+
+# Reference-Level Explanation
+[reference-level-explanation]: #reference-level-explanation
+
+[Link to paper](https://www.jojolepro.com/event_chaining.pdf)
+
+# Drawbacks
+[drawbacks]: #drawbacks
+
+[Link to paper](https://www.jojolepro.com/event_chaining.pdf)
+
+# Rationale and Alternatives
+[rationale-and-alternatives]: #rationale-and-alternatives
+
+[Link to paper](https://www.jojolepro.com/event_chaining.pdf)
+
+# Prior Art
+[prior-art]: #prior-art
+<details>
+<summary>Discuss previous attempts, both good and bad, and how they relate to this proposal.</summary>
+The currently EventRetrigger type in Amethyst was the first proof of concept we did at implementing event chains.
+We only used it in the UI crate to get a basic idea of how this can work.
+
+After this, I implemented an example UiDriver in a [fork](https://github.com/jojolepro/amethyst/tree/eventchain) and it worked just fine.
+</details>
+
+# Unresolved Questions
+[unresolved-questions]: #unresolved-questions
+<details>
+<summary>Additional questions to consider</summary>
+The main unresolved question that remains is how we will make
+the Systems/Drivers register to the EventChannels.
+
+We have the possibility of doing it automatically in a SystemDesc,
+but this doesn't work with Pausable Systems.
+</details>
+
+Copyright 2020 Joël Lupien