This documents our latest thinking on Mu languages. At a high level,
there are three classes of language at play:
1. Mu Metadata Languages (MuML): these are the high-level language
subsets that a programmer uses to specify Mu modules, etc. Examples
include MuJS, MuPy, MuRu, and MyGo, each representing a deterministic
subset of JavaScript, Python, Ruby, and Go, respectively.
2. Mu Intermediate Language (MuIL): this is the intermediate form that
all of the above compile down to. It is capable of representing
computations like functions, conditionals, and basic expressions like
string concatenation, etc. This is fully statically analyzable and
can be used to create deterministic plans and topology graphs.
3. Mu Graph Language (MuGL): this is the "final" form in which any Mu
service topology is represented. It never contains computations and
is merely a metadata description of services-as-nodes, dependencies-as-
edges, and all known properties. In the planning form, it may contain
"holes" because output properties aren't known until execution has
occurred, while in the actual applied form, those holes have been
plugged. MuGLs can be diffed, and a MuGL can be generated from an
existing live environment (for bootstrapping and/or drift analysis).
There are several TODOs in here, but this is braindump of where we're at.
