WorkflowKit

WorkflowKit provides essential Ruby gems for managing business processes (BPMN), rules (DMN), and expressions (FEEL); keeping your apps clean, organized, and maintainable. These gems are light-weight with minimal dependencies and are based on open standards.

FEEL

FEEL expressions are safe and side-effect free. They are ideal for capturing business logic for storage in a database or embedded in DMN or BPMN documents for execution.

Here is a simple example of evaluating a feel expression:

FEEL.evaluate('"👋 Hello " + name', variables: { name: "World" })
# => "👋 Hello World"

The gem can be used to evaluate unary expressions too:

FEEL.test(3, '<= 10, > 50'))
# => true

See the FEEL README and tests for more examples and documentation.

DMN

DMN (Decision Model and Notation) is a standard for defining and executing business rules. DMN uses FEEL to evaluate expressions in the decision tables.

To evaluate a DMN decision table:

variables = {
  violation: {
    type: "speed",
    actual_speed: 100,
    speed_limit: 65,
  }
}
result = DMN.decide('fine_decision', definitions_xml: fixture_source("fine.dmn"), variables:)
# => { "amount" => 1000, "points" => 7 })

See the DMN README and tests for more examples and documentation.

Learn more about the DMN and FEEL Specs. Note: this gem implements a subset of the DMN 1.3 specification.

BPMN

BPMN manages the flow of activities within a process, DMN and FEEL manages the decision logic that drives those activities.

Processes are made of a series of tasks. The engine supports the following task types:

UserTask (manual): requires a signal to continue.
ServiceTask (automated): instantiates a type defined in the task definition and invokes call on it.
BusinessRuleTask (automated): evaluates the decision_id (expects dmn source to be included in the context).
ScriptTask (automated): evaluates the FEEL expression in the script property.

To start the process, initialize with the BPMN and DMN source files, then call start.

sources = [
  File.read("hello_world.bpmn"),
  File.read("choose_greeting.dmn")
]
execution = BPMN.new(sources).start

It's often useful to print the process state to the console.

execution.print

HelloWorld started * Flow_080794y

0 StartEvent Start: completed * out: Flow_080794y
1 UserTask IntroduceYourself: waiting * in: Flow_080794y
2 BoundaryEvent EggTimer: waiting

What makes the BPMN gem unique is the ability to save the state of a process until a task is complete.

# Returns a hash of the process state.
execution_state = execution.serialize

# Now we can save the execution state in a database until a user submits a form (UserTask)
# or a background job completes (ServiceTask)

# Restores the process from the execution state.
execution = BPMN.restore(sources, execution_state:)

# Now we can continue the process by `signaling` the waiting task.
step = execution.step_by_element_id("IntroduceYourself")
step.signal(name: "Eric", language: "it", formal: false, cookie: true)

This continues until the process is complete.

HelloWorld completed *

{
  "name": "Eric",
  "language": "it",
  "formal": false,
  "cookie": true,
  "choose_greeting": {
    "greeting": "Ciao"
  },
  "choose_fortune": "A foolish man listens to his heart. A wise man listens to cookies.",
  "message": "👋 Ciao Eric 🥠 A foolish man listens to his heart. A wise man listens to cookies."
}

0 StartEvent Start: completed * out: Flow_080794y
1 UserTask IntroduceYourself: completed { "name": "Eric", "language": "it", "formal": false, "cookie": true } * in: Flow_080794y * out: Flow_0t9jhga
2 BoundaryEvent EggTimer: terminated
3 ParallelGateway Split: completed * in: Flow_0t9jhga * out: Flow_0gi9kt6, Flow_0q1vtg3
4 BusinessRuleTask ChooseGreeting: completed { "choose_greeting": { "greeting": "Ciao" } } * in: Flow_0gi9kt6 * out: Flow_1652shv
5 ExclusiveGateway WantsCookie: completed * in: Flow_0q1vtg3 * out: Flow_0pb7kh6
6 ServiceTask ChooseFortune: completed { "choose_fortune": "A foolish man listens to his heart. A wise man listens to cookies." } * in: Flow_0pb7kh6 * out: Flow_1iuc1xe
7 ParallelGateway Join: completed * in: Flow_1652shv, Flow_1iuc1xe * out: Flow_0ws7a4m
8 ScriptTask GenerateMessage: completed { "message": "👋 A foolish man listens to his heart. A wise man listens to cookies." } * in: Flow_0ws7a4m * out: Flow_0gkfhvr
9 EndEvent End: completed * in: Flow_0gkfhvr

See the BPMN README and tests for more examples and documentation.

Learn more about the BPMN Spec.

License

These gems are available as open source under the terms of the MIT License.

Developed by Connected Bits

feel

Development

Runtime

WorkflowKit

FEEL

DMN

BPMN

License