RNT is going for a route of a microkernel, and here is one use case
for its servers: imagine a subsystem A and subsystem B. Each register
an evaluator and has their specific program image execution from their
own server, operating under an RNT supervisor. A program image from
subsystem A should be able to invoke and interop with programs from B,
as they both share the common ephemeral relation protocol.

A more concrete case that is warranted is Sakura and Karuta. Here is a
brief introduction of what each is:

- Sakura :: A purely relational algebra system that performs strictly
  first order logic for data retrieval, and integrates other
  subsystems for DDL, DML and version control.
- Karuta :: A logic language targeting the BEAM, similar to Prolog,
  but that operates under microKanren.

Karuta compiles programs to a /.beam/ format, and embeds them with two
additional /.lfe/ files: karuta.lfe & sakura.lfe, and executes them with
/play/ lfescript that glues all together.

Our goal with the subsystem integration is to make Karuta produce
Sakura programs (it already does), that can be loaded as program
images on RNT, executing through the registered evaluator.