Transform DSL | OpexFlow

A tiny, statement-based language evaluated natively against the in-memory CanonicalMachineData struct — the lowest-latency path for filters and field math.

The OpexFlow DSL is a tiny, statement-based language evaluated natively against the in-memory event struct. It exists for the 90% of transforms that are filters and field math, where spinning up a JS interpreter per event is pure waste.

DSL programs live inline (script_inline) or in a file (script), exactly where a JS script would. Pick the backend with backend: "dsl".

Syntax overview

A program is a list of statements, one per line. Comments start with #. There are exactly three statements:

# a complete DSL program
when metadata.temp > 80 || metadata.vib > 5.0   # keep iff true; else DROP the record
set metadata.alert = true                 # mutate a field
set status.state = "alarm"                 # ... another field

Statement	Meaning
`when <expr>`	Filter. The record is kept iff `<expr>` is true; otherwise it’s dropped (nothing flows to sinks). At most one `when` per program.
`set <path> = <expr>`	Mutate a field. Targets: `metadata.*` (nested, auto-created), `status.state`, `status.alarmCode`, `status.alarmMessage`, `machine.id`, `machine.name`.
`drop`	Drop the record unconditionally. Equivalent to JS `return null`.

If a program has no when and no drop, the (possibly mutated) record always passes through to its sinks.

Expressions & operators

Operator	Description
`
`== != < <= > >=`	Comparisons, return booleans. Numeric first, string ordering as fallback.
`+ - * /`	Arithmetic. `+` also concatenates two strings.
`( )`	Grouping.

Literals

42   3.14             # numbers (float)
"running"            # string
true  false  null    # booleans, null

Paths

Paths read directly from CanonicalMachineData. Dotted, with numeric segments indexing arrays:

Path	Reads
`source`	Origin protocol (`modbus`, `opcua`, `http`, …).
`machine.id` / `machine.name`	Stable machine id / display name.
`status.state`	`running` \| `idle` \| `alarm` \| `offline`.
`status.alarmCode` / `status.alarmMessage`	Active alarm (or null).
`spindle.speed` / `spindle.load`	Spindle readings (null if no spindle).
`axes.<i>.position`	Indexed axis position (also `.name`, `.unit`).
`metadata.<key>...`	Free-form nested JSON, where sensors like `temp`, `vib`, `rpm` live.

Examples

Conditional alert (filter + flag)

when metadata.temp > 80 || metadata.vib > 5.0
set metadata.alert = metadata.temp > 80 || metadata.vib > 5.0

Force alarm state on high load

when spindle.load > 90
set status.state = "alarm"
set status.alarmMessage = "spindle overload"

Unit conversion + nested metadata

set metadata.temp_f = metadata.temp_c * 9 / 5 + 32
set metadata.flags.hot = metadata.temp_c > 60

Pass only running machines

when !(status.state == "offline")

DSL cheat sheet

when expr            keep iff true
set path = expr      mutate field
drop                 drop the record
metadata.x           sensor values
status.state         run state
|| && !              boolean logic
== != > <            comparisons
+ - * /              arithmetic
# comment            one per line
"str" / true / null

Try it: live REPL

Edit the record and the program, then run. This is an in-browser evaluator of the documented DSL subset operating on the record object, no server round-trip. The interactive REPL is available in the running connector’s in-app docs; the reference behavior is fully covered by the syntax, operators, and examples above.