Add some notes about design goals

Author: mikeshardmind

readme.md

@@ -6,3 +6,33 @@ This contains various async utility functions I've written
 
 Things now have initial documentation, but no rendered docs site, examples, or
 prose yet.
+
+# Design goals
+
+## The obvious use should be correct
+
+Examples of this:
+
+- Any caveats should be documented prominently.
+- Internally wrapping user functions should retain features
+  such as laziness and backpressure (see: gen_transform.py)
+- If the library can't correctly wrap behavior, it shouldn't wrap that behavior.
+
+## Pay for only what you use
+
+This library is designed so that you only pay for the abstractions you use, without
+breaking potential interaction with other library uses.
+
+This includes:
+
+- imports are namespaced, (inspect import is incurred only if you import task_cache).
+- typing imports are resolvable at runtime.
+- typing imports are lazily evaluated (see _typings.py).
+- Some classes/functions with only minor variations are intentionally duplicated partially.
+- possibly more things I'm forgetting right now.
+
+## Task cancellation should only ocur where obvious and documented
+
+There's not much further to say about this goal right now, but this
+should be expanded on later in the WIP accompanying guide on making
+concurrent systems written in python fault tolerant at scale.