statemachine-dsl

Statemachine DSL

A small textual language for describing finite state machines: a named machine, the events it recognizes, optional commands, an initial state, and a set of states connected by transitions.

File structure

A file is one machine, in this fixed order:

statemachine <Name>

events
    <eventName>
    <eventName>

commands
    <commandName>

initialState <StateName>

state <StateName>
    actions { <commandName> }
    <eventName> => <TargetStateName>
end

• statemachine <Name> — required header naming the machine. <Name> is an identifier ([_a-zA-Z][\w_]*).
• events — optional block listing one or more event names, one per line (whitespace separated).
• commands — optional block listing one or more command names.
• initialState <StateName> — required; must reference a state defined in the file.
• state ... end — zero or more state definitions.

Syntax (EBNF)

statemachine_file = "statemachine", identifier,
                    [ events_block ], [ commands_block ],
                    "initialState", state_ref,
                    { state } ;

events_block      = "events", { event_name } ;
commands_block    = "commands", { command_name } ;

state             = "state", identifier,
                    [ actions_clause ],
                    { transition },
                    "end" ;

actions_clause    = "actions", "{", { command_ref }, "}" ;
transition        = event_ref, "=>", state_ref ;

event_name        = identifier ;
command_name      = identifier ;
event_ref         = identifier ;   (* must match a declared event *)
command_ref       = identifier ;   (* must match a declared command *)
state_ref         = identifier ;   (* must match a defined state *)

identifier        = letter, { letter | digit | "_" } ;
letter            = "A" | "B" | ... | "Z" | "a" | "b" | ... | "z" ;

There is no closing end for the whole machine — only each state block ends with end.

States and transitions

Each state is a state <Name> ... end block containing: