MagmaScript expressions (mapping service)

Using MagmaScript expressions

Introduction

In the mapping service, MagmaScript is used to define the mapping algorithms. The expression format is based on the Magma JavaScript API.

Examples

The following expression returns true when the value of attribute 'myAttributeName' of an entity only contains alphanumberic characters:

regex('^[a-zA-Z0-9]+$',{myStringAttributeName})

In this example:

  • '$(...)' is the selector

  • 'myStringAttributeName' is an attribute name

  • 'matches' is a chaining operation

  • 'value' is a terminal operation

Chaining operations allows you to express complex expressions:

$('myIntAttributeName').gt(3).and($('myIntAttributeName').lt(6)).value()

Chaining operations

Numerical operations

OperatorParametersExampleDescription

plus

Number

$('height').plus(100).value()

height + 100

pow

Number

$('height').pow(100).value()

height ^ 100

times

Number

$('height').times(100).value()

height * 100

div

Number

$('height').div(100).value()

height / 100

gt

Number

$('height').gt(100).value()

height > 100

lt

Number

$('height').lt(100).value()

height < 100

ge

Number

$('height').ge(100).value()

height >= 100

le

Number

$('height').le(100).value()

height <= 100

Binary operations

OperatorParametersExampleDescription

eq

Number

$('height').eq(100).value()

height === 100

matches

Regex

$('name').matches(/^[a-z0-9]+$/i).value()

name is alphanumerical

isNull

-

$('height').isNull().value()

height === null

not

-

$('hasEars').not().value()

!hasEars

or

Expression

$('male').or($('female')).value()

male

and

Expression

$('female').and($('pregnant')).value()

female && pregnant

Unit operations

OperatorParametersExampleDescription

unit

Unit

$('height').unit('cm')

Sets the current value unit to cm

toUnit

Unit

$('height').unit('m').toUnit('cm').value()

Converts the current value based on the change in units

Other

OperatorParametersExampleDescription

age

-

$('dateOfBirth').age().value()

Returns the age based on the date of birth and the current year

map

Object

$('data').map({0:1, 1:2}).value()

Maps categories to each other

group

Array

$('age').group([18, 35, 50, 75]).value()

Produces left-inclusive ranges with the given boundaries, i.e. (-∞, 18), [18, 35), [35, 50), [50, 75), [75, +∞) and then returns the interval that the attribute value is in, i.el '18-35'

attr

String

$('person').attr('name').value()

Returns the value of an attribute of a reference

Terminal operations

OperatorParametersExampleDescription

value

-

$('height').value()

JavaScript value

Special case: reference types

If an attribute is a reference type (MREF, XREF, CATEGORICAL, CATEGORICAL_MREF) you can use the 'attr' operation, to access the values of different columns in the row being referenced. E.g. $('cookie').attr('name').value() gives you the value of the name column inside the table being referenced by the cookie column. See below for a more detailed example.

Imagine table A referencing table B.

Table A has 2 columns: id, cookie. Table B has 3 columns: id, name, tastiness.

The cookie column in table A references table B.

Table A

idcookie

A

1

Table B

idnametastiness

1

Chocolate chip

9/10

Expressions allow you to do the following

// Expressions are based on table A

$('cookie').value() // results in '1'
$('cookie').attr('id').value() // results in '1'
$('cookie').attr('name').value() // results in 'Chocolate chip'
$('cookie').attr('tastiness').value() // results in '9/10'

In the following case, we have Table A which has multiple references to Table B e.g. an MREF

Table A

idcookie

A

1,2,3

Table B

idnametastiness

1

Chocolate chip

9/10

2

Strawberry cookie

10/10

3

Banana cookie

7/10

// Expressions are based on table A

$('cookies').map(function (cookie) {
    // Pick one of the following
    return cookie.value()                   // results in ['1', '2', '3']
    return cookie.attr('id').value()        // results in ['1', '2', '3']
    return cookie.attr('name').value()      // results in ['Chocolate chip', 'Strawberry cookie', 'Banana cookie']
    return cookie.attr('tastiness').value() // results in ['9/10', '10/10', '7/10']
}).value()

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