mal#

Pure OCaml implementation of the CCSDS Mission Operations Message Abstraction Layer (MAL), as defined in CCSDS 521.0-B-1.

Overview#

MAL is a service-oriented architecture framework for mission operations. It provides a standard set of interaction patterns and data types that decouple service consumers from service providers, allowing mission operations services to be deployed over different transport technologies.

Six interaction patterns are supported: Send, Submit, Request, Invoke, Progress, and Pub-Sub. Each prescribes a fixed sequence of typed messages between consumer and provider.

Installation#

Install with opam:

$ opam install mal

If opam cannot find the package, it may not yet be released in the public opam-repository. Add the overlay repository, then install it:

$ opam repo add samoht https://tangled.org/gazagnaire.org/opam-overlay.git
$ opam update
$ opam install mal

Usage#

let run () =
  (* Create an in-memory transport for testing *)
  let provider = Mal.Mem_transport.create "mal:provider" in
  let consumer = Mal.Mem_transport.create "mal:consumer" in
  (* Build a Request message *)
  let tid = Mal.next_transaction_id () in
  let msg =
    Mal.header
      ~uri_from:"mal:consumer" ~uri_to:"mal:provider"
      ~interaction_type:Mal.Request ~stage:Mal.Request_stage
      ~transaction_id:tid ~area:1 ~service:1 ~operation:1
      ~body:"ping" ()
  in
  (* Send and dispatch *)
  let _ = Mal.Mem_transport.send consumer msg in
  (match Mal.Mem_transport.recv provider with
   | Ok received -> Printf.printf "Got: %s\n" received.Mal.body
   | Error code -> Fmt.pr "Error: %a\n" Mal.pp_error_code code);
  Mal.Mem_transport.close provider;
  Mal.Mem_transport.close consumer

API Overview#

Interaction patterns -- Send, Submit, Request, Invoke, Progress, Pub_sub
Data types -- blob, identifier, uri, time, fine_time, duration
Message header -- Full routing metadata: URIs, QoS, session, transaction ID
Service registry -- register_area, register_handler, dispatch
Transport module type -- Abstract transport binding (send, recv, close)
Mem_transport -- In-memory transport for testing and local use
header, next_transaction_id, validate_stage -- Helpers

References#

CCSDS 521.0-B-1 -- Mission Operations Message Abstraction Layer
CCSDS 520.0-G -- Mission Operations Services Concept (Green Book)

Licence#

ISC License. See LICENSE.md for details.

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