Types

Introduction

The RIDDL language allows users to define data types. Definitions of types are more limited in RIDDL than in programming languages on purpose. The type system must be easily understandable by non-programmers as the domain engineer or domain expert is likely the most frequent user.

Predefined Types

RIDDL supports several predefined types that just “exist” because they are fundamental and well understood in any targeted computing environment. These predefined type names can be used anywhere that a type definition is needed, for example in a field of an entity’s state definition see here

The predefined types are:

String - a sequence of characters of any length
Boolean - a binary value for true/false logic
Number - a numeric value either integer or decimal
Integer - a numeric value that excludes fractional parts
Decimal - a numeric value that includes fractional parts
Real - a real number
Id - a globally unique identifier
Date - a date value
Time - a time of day value
DateTime - a date and a time value together
TimeStamp - a date and time combined with at least millisecond accuracy
Duration - the amount of time between a start and stop time
LatLong - a position on earth
Nothing - a type that cannot hold a value
URL - a uniform resource locator of any scheme

Named Type Definitions

In addition to the predefined types, RIDDL supports the definition of new types using a name and a type expression with this syntax:

type name = <type-expression>

When defining values, one must use a named type defined with the type keyword. This enforces legibility by naming every type expression.

Type Expressions

RIDDL supports a variety of type expressions for defining named types. The following sections define the kinds of expressions allowed.

Renames

It is possible to rename a predefined or previously defined type as another type name. This is common to increase domain applicability of the name of a predefined type. For example,

type FirstName = String // rename a predefined type for clarity

might be used to make it clear that the intended use of the String value is to provide a person’s first name.

Bounded Strings

The predefined types allow use of unbounded strings but when you want to fix the minimum or maximum length of a string, it may only be used in a type expression. The expression String(<min>, <max>) can be used to define such a type. Both <min> and <max> are optional. <min> defaults to 0, and max defaults to infinite. For example;

type FirstName = String(2, 30) // string between 2 and 30 chars inclusive
type LastName = String(,30) // string between 0 and 30 chars
type Unbounded = String(,) // unbounded, same as just "String"

Patterns

When you need a string to conform to a regular expression, you can use the Pattern type expression. The expression Pattern(<regex>) will define a string that validates its content according to <regex> which must be a quoted Scala regular expression. If assignment to the string does not match the<regex> then an InvalidateEstateException will be generated. For example, here’s a pattern for extracting the three components of a North American telephone number:

type NATelephoneNumber = pattern("\(?([0-9]{3})\)?-?([0-9]{3})-?([0-9]{4})")

Range

The predefined types allow the use of unbounded integers but when you want to constrict the range of values, you need a Range type expression. The expression Range(<min>,<max>) will define an integer value whose range is restricted to the <min> and <max> values provided. As with [bounded strings](#Bounded Strings), the <min> and <max> values are optional and default to 0 and infinity respectively. For example:

type Percent = range(,100) // only value 0 to 100 inclusive

Restricted Scheme URL

The predefined types allow the use of any URL, but when you want to restrict the URL to a specific scheme (e.g. “http”, “mailto”) then you can use the URL type expression. The expression URL(<scheme>) specifies a URL that is restricted to the <scheme> specified. For example:

type HTTPS_URL = url("https")

Unique Identifier

To define a type that uniquely identifies a runtime entity the Id type expression can be used. It requires a pathIdentifier parameter which specifies the full path (from the root domain) to the runtime entity. For example:

type ModelXRef = Id(Autos.Tesla.ModelX)