Business-Rules Engine
===========

Condition Symbols

- Column Value: $$ example DateDiff($$,@now)
- variable symbol: $example: $caseId this is needed since we allow multi words operations like starts with
- Is null value or empty: Null or Empty
- Any Value: -

- All types:
- null or empty
- not null
- true or false

Type	Syntax	Examples
Numbers	value	500
	compare operator	>500
		<500
		between 500 and 700
String	value	Low-Income
	Quoted Value	'Low-Income'
	string operators	starts with 'Low'
		ends with 'Income'
		contains 'Income'
		not 'Low-Income'
Date	Quoted value	'2020/12/01'
	Date operators	after '2020/12/01'
		>30 days
		<10 years
		contains 'Income'
		not 'Low-Income'


Introduction

Is a Business Rules Engine supporting DMN Decision Tables.
Allowing developers to integrate Rules into JavaScript or Node.js applications.

This solution utilizes deterministic rules vs Rete based solutions that are non-deterministic.

This package is designed specifically for Node.js and TypeScript

As an example of Decisition Table
!Example

!Anatomy

Usage

$3

Decision table can be defined as a JSON or CSV file

$3

To invoke the above example
``js
const Rules=requires('./business-rules.json')'
const dt= Rules.load('client-category);
let result=dt.run({type:'Private', deposit: 500 , netWorth: 500});

console.log(result.category);
`

$3

`js
const tester=Rules.loadTest('./client-category-tests.json');
let results=tester.run();
console.log(results.summary);
`
!tests

$3

Rule Syntax

$3

#### Expression Language

#### Simple Conditions shortcuts

- Literal values with or without quotes, so "high" and high are acceptable

- coditional operators and functions without referencing the variable like >500

- Empty Condition or - indicates all values are true
- For numeric variables:
- > 500
- between 500 and 700
- For Date variables, functions like:
- > 30 days , > 50 minutes , < 10 years etc.
- before '2018/01/01' or after '2018/03/01'
- between '2018/01/01' and '2019/12/31'
-
#### Complex Conditions
- And , Or and Not operators, brackets () can also be used
-
- complex operations and functions can reference the variable using @ symbol

$3

Output expressions can use the full expression language and reference any input or ouput variable.

Expression Engine

`js

const exp=new Expression(2+3*4);
const result= expr.evaluate();
console.log(result);

`
Expressions are compiled into AST
`js
const exp=new Expression(2+3*4);
const compiled= expr.compile();

// or reloaed

const expr=Expression.load(compiled);
const result= expr.evaluate();

console.log(result);
`

Language Constructs

Literals

- Strings: 'John'
- Numbers: 123.25

Words

salary

customer.address

Operators

The package already defines a set of operators but you can add your own

$3

+ -' * / etcs.

$3

between is defined as a word operator

Functions

Keywords

The following literals are defined as Keywords

-true
-false
-null