Module Versioned_rpc

module Versioned_rpc: Versioned_rpc

• The caller is responsible for managing versions and dispatches to callees that are written in a version-oblivious way.

  The proto-typical example of this scenario is a commander that needs to call out to many assistants for that same system. In this scenario, the assistants each implement a single version of the rpc and the commander has to take this into account.

• The callee is responsible for managing versions and is called by

  The proto-typical example of this scenario is an assistant from one system calling out the commander of another system In this scenario, the assistants each know a single version of the rpc to call and the commander has to implement them all.

In each scenario, it is desirable that the party responsible for managing versions be coded largely in terms of a single "master" version of the types involved, with all necessary type conversions relegated to a single module. Versioned_rpc is intended for implementing such a module.

Type coercions into and out of the model go in the directions indicated by the following diagram:

       Caller converts                 Callee converts
       ===============                 ===============

           caller                        callee
           |       callee                |      callee
           |       |       caller        |      |       callee
           |       |       |             |      |       |
        ,-->-- Q1 --> R1 -->-.      Q1 -->-.    |    ,-->-- R1
       /                      \             \   |   /
      Q --->-- Q2 --> R2 -->-- R    Q2 -->-- Q --> R --->-- R2
       \                      /             /       \
        `-->-- Q3 --> R3 -->-'      Q3 -->-'         `-->-- R3
 

module Caller_converts: sig .. end

module Callee_converts: sig .. end

module Menu: sig .. end