Operator Catalogue

Cameleon ships with 13 operators across three standard libraries. This page is the functional reference — what each operator does, what it expects, what it produces.

For implementation details (run/rollback signatures, code), see the technical docs in doc/architecture/libs/.

Overview

Operator	Library	Description	Inputs	Outputs	Firing	Config
Source	std-io	Emits a static configured value	—	`out_data` DataString	ANY	`value`
Sink	std-io	Consumes data (terminal output)	`in_data` DataString	—	ANY	—
FileLoader	std-io	Loads a file via browser dialog	—	`out_data` Binary	ANY	`accept`
Fork	std-struct	Duplicates input to two outputs (AND-split)	`in_data` Any	`out_a` `out_b` Any	ANY	—
Join	std-struct	Waits for all inputs, passes first through (AND-join)	`in_a` `in_b` Any	`out_data` Any	ALL	—
Merge	std-struct	First arrived passes through (XOR-join)	`in_a` `in_b` Any	`out_data` Any	ANY	—
Gate	std-struct	Routes input based on a boolean condition (XOR-split)	`in_data` Any, `in_condition` DataBool	`out_true` `out_false` Any	COND	—
Barrier	std-struct	Waits for all inputs, routes each to paired output	`in_a` `in_b` Any	`out_a` `out_b` Any	ALL	—
Transform	std-data	Converts any data to string	`in_data` Any	`out_data` DataString	ANY	—
Format	std-data	Concatenates two strings with separator	`in_main` `in_meta` DataString	`out_data` DataString	ALL	`separator`
JSONParse	std-data	Parses a JSON string into an object	`in_data` DataString	`out_data` DataJSON	ANY	—
JSONStringify	std-data	Serializes an object to JSON string	`in_data` DataJSON	`out_data` DataString	ANY	`pretty`
Template	std-data	Replaces {{key}} placeholders with values	`in_template` DataString, `in_data` DataJSON	`out_data` DataString	ALL	—

Firing policies : - ANY — fires when at least one input is NEW (or no inputs for sources) - ALL — fires when all inputs are NEW - COND — fires when a custom condition is met (see operator details)

I/O — std-io

Entry and exit points of a pipeline. Data sources and sinks.

Source

Emits a static value configured in advance. This is the most common entry point of a composition — it injects an initial value into the pipeline without receiving anything.

No inputs — Source fires when all its outputs are EMPTY (ready to receive).

Output	Type	Label
`out_data`	DataString	data

Config

Parameter	Type	Default
`value`	string	`"Hello from Source"`

Sink

Consumes data and logs it. This is the terminal output of a pipeline — nothing comes out of a Sink. Use it to observe results in the CVM Log.

Input	Type	Label
`in_data`	DataString	data

No outputs, no config.

FileLoader

Opens a file picker dialog and loads the selected file as binary data. Browser only — does not work in CLI mode. Async: the operator stays in RUNNING state until the user selects a file.

Supports cancellation via the CVM abort signal.

No inputs — FileLoader fires like a source.

Output	Type	Label
`out_data`	Binary	data

Config

Parameter	Type	Default
`accept`	string (MIME filter)	`"/"`

Control Flow — std-struct

Routing, merging, and synchronization. Pure token routing — no data transformation. All plug types are Any, meaning they accept any data type.

Aligned with standard workflow patterns (van der Aalst, WCP).

Fork

Duplicates a single input to two outputs. Both branches receive the same data. This is the AND-split pattern (WCP-2): all branches are activated.

Input	Type	Label
`in_data`	Any	data

Output	Type	Label
`out_a`	Any	A
`out_b`	Any	B

Firing : ANY — fires as soon as in_data is NEW.

Join

Synchronization barrier — waits for both inputs before producing output. Passes in_a through to out_data; in_b is consumed but its value is discarded. This is the AND-join pattern (WCP-3).

Input	Type	Label
`in_a`	Any	A
`in_b`	Any	B

Output	Type	Label
`out_data`	Any	data

Firing : ALL — fires only when both in_a AND in_b are NEW.

Merge

First-arrived passes through. If both inputs arrive simultaneously, in_a has priority. This is the XOR-join pattern (WCP-5): only one branch is consumed per firing.

Input	Type	Label
`in_a`	Any	A
`in_b`	Any	B

Output	Type	Label
`out_data`	Any	data

Firing : ANY — fires as soon as at least one input is NEW.

Gate

Conditional routing — examines a boolean condition and routes the input data to one of two outputs. This is the XOR-split pattern (WCP-4).

Input	Type	Label
`in_data`	Any	data
`in_condition`	DataBool	condition

Output	Type	Label
`out_true`	Any	true
`out_false`	Any	false

Firing : COND — custom rule: fires only when both in_data AND in_condition are NEW. This is stricter than ALL because Gate uses a canFire() override.

Routing rule : if in_condition is truthy, data goes to out_true; otherwise to out_false. The unused output stays EMPTY.

Barrier

Synchronized passthrough — waits for all inputs, then routes each to its paired output. This is equivalent to Join + Fork but preserves the identity of each input: in_a goes to out_a, in_b goes to out_b.

Extension Cameleon — no standard WCP equivalent.

Input	Type	Label
`in_a`	Any	A
`in_b`	Any	B

Output	Type	Label
`out_a`	Any	A
`out_b`	Any	B

Firing : ALL — fires only when both in_a AND in_b are NEW.

Data — std-data

Data transformation and formatting. Converts, formats, parses, and templates data flowing through the pipeline.

Transform

Converts any data to a string representation. Simple type conversion — equivalent to calling String(value).

Input	Type	Label
`in_data`	Any	data

Output	Type	Label
`out_data`	DataString	data

Firing : ANY.

Format

Concatenates two strings with a configurable separator. Useful for building labels, log lines, or display strings from two parts.

Input	Type	Label
`in_main`	DataString	main
`in_meta`	DataString	meta

Output	Type	Label
`out_data`	DataString	data

Firing : ALL — waits for both inputs.

Config

Parameter	Type	Default
`separator`	string	`" \	"`

JSONParse

Parses a JSON string into a structured object. If the input is not valid JSON, the operator transitions to FAILED state.

Input	Type	Label
`in_data`	DataString	data

Output	Type	Label
`out_data`	DataJSON	data

Firing : ANY.

Error : FAILED if input is not valid JSON.

JSONStringify

Serializes a structured object to a JSON string. Optionally formats with indentation for readability.

Input	Type	Label
`in_data`	DataJSON	data

Output	Type	Label
`out_data`	DataString	data

Firing : ANY.

Config

Parameter	Type	Default
`pretty`	boolean	`false`

When pretty is true, the output is indented with 2 spaces.

Template

String interpolation — replaces {{key}} placeholders in a template string with values from a JSON object. Missing keys are replaced with an empty string.

Input	Type	Label
`in_template`	DataString	template
`in_data`	DataJSON	data

Output	Type	Label
`out_data`	DataString	data

Firing : ALL — waits for both the template and the data.

Example : template "Hello {{name}}" + data {"name": "Alice"} → "Hello Alice".