model-lang/docs/overview.md

what is modellang?

modellang is an event modeling language built with ease of use and flexibility in mind. The driving concept behind this is the separation of model description into two distinct parts: behaviors and interactions. To wit, let us describe a model where one task sends messages and another task will then receieve them:

SYSTEM: task_a = send*;
SYSTEM: task_b = receive*;

INTERACTION: task_a:send -> task_b:receive;

modellang is not just an ergonomic language, though. Its trace generator is able to simulate all possible scenarios of a model within a small scope, producing a queryable set of results.

language

A modellang model is composed of systems of behaviors, interactions between the systems, and triggers that control properties.

A system is a top-level event, and is where trace generation starts. Can consist of composite events (behaviors) or atomic events.

SYSTEM: sys = behavior_pattern atomic_event;
BEHAVIOR: behavior_pattern = expanded detail;

An interaction can fall into one of three categories: relations. pre-conditions, and post-conditions:

• the two relations supported are "->" (order) and "==" (join)
• pre- and post-conditions guarantee your resultant traces abide by certain rules
• an interaction is a condition iff one operand of the "->" is an expression and the other is a selector; two selector operands makes for a relation; and two expressions makes for an invalid interaction

• selectors (also found in triggers) are patterns just like system and behavior definitions, but come with a prepended system: to inform the generator where to look for the pattern

  INTERACTION: sys:before -> other_sys:after;
  INTERACTION: sys:shared_event == other_sys:shared_event;
  INTERACTION: property > 5 -> thing:happens_only_above_5;
  INTERACTION: thing:never_drops_below_three -> other_property >= 3;
  

A trigger is a chunk of code that will execute whenever the specified selector pattern occurs during trace generation.

WHEN: sys:event1 event2 { property++ };

Behavior patterns are the way in which events are described.

SYSTEM: sequence = a whitespace delimited list of events occurring in order;
SYSTEM: group = you can even (wrap stuff into groups);
SYSTEM: alternation = a (pipe | vertical bar | stick) delimited list of sequences;
BEHAVIOR: quantifiers = none_or_more* one_or_more+ none_or_one?;
BEHAVIOR: ranges = do_exactly_n_times{n} do_at_least_n_times{n,} do_n_to_m{n,m};

Whitespace is insignificant.
Comments are C-style.