node pico-engine quickstart

This page will guide you through the steps necessary to obtain and operate your own Kinetic Rules Engine (KRE).

Learning Objectives

After completing this quickstart lesson, you will:

• understand important concepts about programming in KRL including ruleset structure^*
• know how to install and operate the node pico-engine
• know how to use the "Engine Rulesets" page to register a ruleset
• know how to add a ruleset to a Pico
• become familiar with using the "My Picos" page to work with your Picos

Concepts

^*This section is copied verbatim from Quickstart (the one for the original KRE system)

Getting started with KRL can be a big leap because there are so many things that are different about programming in KRL:

• KRL is a rule-based language. 
• KRL primarily follows an event-based programming model. 
• KRL programs execute with a cloud-based model; there is no way to execute them from the command line.
• KRL programs are loaded from the cloud using HTTP. 
• KRL programs execute in a system where identity is pervasive; all events are raised on behalf of a specific entity.
• KRL programs have built-in, entity-specific persistent storage; there is no need for external databases.

The result of these properties is a programming model that more closely resembles programming cloud-based persistent objects than anything else. We call these persistent computational objects "picos". 

KRL is executed by your instance of the node pico-engine, an open-source, cloud-based rule processing system. All of the properties listed above are present in any KRE system. 

Install and run the node pico-engine

Prerequisite: you will need to install node (also known as Node.js) on your machine. It includes npm, the node package manager.

$ npm install -g pico-engine
$ PORT=8084 pico-engine
http://localhost:8084

In the example above, port number 8084 was chosen. By default, if you run the command `pico-engine` without setting the environment variable, port 8080 will be used.

Note that the web server displays the URL of its document root, ex. "http://localhost:8084" and then continues to run. As we will see later, messages will be logged to this console.

Create a Pico

Visit the default web page of your web server. As this page loads, it will perform a bootstrap sequence, which creates a Pico, known as "Owner Pico" and then registers and installs two rulesets.

Subsequent visits to the same page will short-circuit the bootstrap (because it's already been done).

Writing KRL

Here is a sample KRL ruleset:

ruleset hello_world {
  meta {
    name "Hello World"
    description <<
A first ruleset for the Quickstart
>>
    author "Phil Windley"
    logging on
    shares hello
  }
 
  global {
    hello = function(obj) {
      msg = "Hello " + obj;
      msg
    }
  }
 
  rule hello_world {
    select when echo hello
    send_directive("say") with
      something = "Hello World"
  }
 
}

Enter the ruleset name "hello_world" into the small box (with placeholder "ruleset id") in the "Engine Rulesets" page (linked from the "Pico Bootstrap" page), and click the "add" button. Then complete the ruleset, and click the "validate" button. When your KRL compiles correctly, you will see a result of "ok" beneath the buttons.

Click on the "register" button. Notice the circle beside the ruleset name. This indicates that the source code has been registered with the pico-engine, but is not yet enabled. Click on the "enable" button.

Finally, click on the "install" button. This causes the pico-engine to compile the KRL and cache the compiled version in the "rulesets" folder. Once this has been done, the ruleset can be added to Picos.

Adding the Ruleset to your Pico

So far, you have installed the ruleset into your pico-engine. But it can't run unless it has been added to a Pico.

Adding a ruleset to a Pico is properly a user function, but as a developer, you are functioning in both user and developer capacities.

View your Owner Pico by visiting the "My Picos" page (linked from the "Pico Bootstrap" page).

Your owner Pico is represented by a rounded rectangle, which is placed on a canvas, allowing you to change its placement.

Click on the rounded rectangle, on your Owner Pico. It expands giving you access to information about it.

The "About" tab will be used in subsequent lessons.

Click on the "Rulesets" tab.

Notice that the name of your ruleset is in a drop-down list. Click the "add ruleset" button to add the ruleset to your Pico.

Notice that you are able to delete the ruleset from the Pico.

Next Steps

Having completed this quickstart, you should continue with Lesson 1. events and queries