Fsystem and Fspec Files

Fault has two different types of files the compiler knows how to read .fsystem files which define the model’s state chart and .fspec files which define model specifications. You can define models to use either a single .fsystem or a single .fspec file, or use an .fsystem file to import multiple .fspec files for more complex systems.

Single Level Imports

Only .fsystem files can import other files. Fault only allows a single level of imports. A model state chart can import specifications. State charts cannot import other state charts. Specifications cannot import state charts or other specifications. This allows models to be broken up into reusable parts, but doesn’t allow circular imports or long dependency chains. In general I’m cynical about the benefits of complex inheritance patterns and over generalized abstractions from OOP. I think such things make code look pretty at the expense of understanding the behavior of that code, which is of greater importance.

classDiagram
    Fsystem <.. cache
    Fsystem <.. orchestrator
    Fsystem : record (cache) 
    Fsystem : manager (orchestrator)
    Fsystem: replCache 
    Fsystem: containerMng
    class cache{
      machine
      lookup()
      release()
      store()
      expire()
    }
    class orchestrator{
      p
      add()
      remove()
      boot()
    }

Layout of a Fsystem File

.fsystem files have a set of required elements and the set of optional elements.

A .fsystem file is the state chart of the entire system being modelled. It’s the high level view of system behavior. Assertions particular to stock/flow behavior should be in the .fspec file where those behaviors are defined if possible so that everything in the .fsystem focuses on the state chart.

The compiler expects a system declaration statement first, followed by any imports, followed by initializing stocks and flows from those imports, followed by the components, then assertions and ending the file with a start block and/or a run block. The run block (if present) always comes last.

flowchart TD
    sysClause[System Declaration] -..- imports[Imports]
    imports ===  globals[Initialize Globals]
    sysClause  -..-  component[Components]
    sysClause -..- assert[Assertions]
    sysClause  -..-  startBlock[Start Block]
    sysClause -..- runBlock[Run Block]
    class imports merOpNode
    class assert merOpNode
    class runBlock merOpNode

Fspec Files

.fspec files have a similar structure to the .fsystem file but a different set of structures can be declared.

A .fspec file defines one complete interaction that determines the transition of the state machine from one state to another. Stocks/Flows can be defined in a .fspec file but not components. Likewise components can be defined in .fsystem but Stock/Flows must be imported.

Single file models in Fault–therefore–are either all state machine, or a specification of a single process.

flowchart TD
    specClause[Spec Declaration] -..- constants[Model Constants]
    specClause  -..-  stocks[Stocks]
    specClause  -..-  flows[Flows]
    specClause -..- assert[Assertions]
    specClause -..- runBlock[Run Block]
    class constants merOpNode
    class assert merOpNode
    class runBlock merOpNode