TerminusDB Data Types

TerminusDB supports a comprehensive set of data types for schema definitions. This reference covers all supported types organized by namespace, including type hierarchy, storage details, and typecasting rules.

For schema definition syntax, see the Schema Reference Guide.

Quick Reference

Namespace	Types	Description
XSD Core	`xsd:string`, `xsd:boolean`, `xsd:decimal`, `xsd:double`, `xsd:float`	Fundamental data types
XSD Integers	`xsd:integer`, `xsd:byte`, `xsd:short`, `xsd:int`, `xsd:long`, unsigned variants	Signed and unsigned integer types with range constraints
XSD Date/Time	`xsd:dateTime`, `xsd:date`, `xsd:time`, `xsd:duration`, and Gregorian types	Temporal data types with timezone support
XSD Strings	`xsd:normalizedString`, `xsd:token`, `xsd:language`, `xsd:Name`, `xsd:NCName`, `xsd:NMTOKEN`	Constrained string types
XSD Binary	`xsd:base64Binary`, `xsd:hexBinary`	Binary data encoding
RDF	`rdf:langString`, `rdf:PlainLiteral`, `rdf:XMLLiteral`	RDF-specific literal types
XDD Extensions	`xdd:coordinate`, `xdd:coordinatePolygon`, `xdd:json`, `xdd:url`, `xdd:email`, `xdd:html`, range types, `xdd:dateTimeInterval`	TerminusDB extension types for specialized data
System	`sys:JSON`, `sys:JSONDocument`, `sys:Dictionary`	System types for JSON and document handling

Type Hierarchy

TerminusDB implements a type hierarchy where child types inherit from parent types. This enables type subsumption—a value of a child type can be used where a parent type is expected.

Example: Text

xsd:anySimpleType
├── xsd:string
│   ├── xsd:normalizedString
│   │   └── xsd:token
│   │       ├── xsd:language
│   │       ├── xsd:NMTOKEN
│   │       └── xsd:Name
│   │           └── xsd:NCName
│   ├── xdd:url
│   ├── xdd:email
│   └── xdd:html
├── xsd:boolean
├── xsd:decimal
│   ├── xsd:integer
│   │   ├── xsd:long
│   │   │   └── xsd:int
│   │   │       └── xsd:short
│   │   │           └── xsd:byte
│   │   ├── xsd:nonNegativeInteger
│   │   │   ├── xsd:positiveInteger
│   │   │   └── xsd:unsignedLong
│   │   │       └── xsd:unsignedInt
│   │   │           └── xsd:unsignedShort
│   │   │               └── xsd:unsignedByte
│   │   ├── xsd:nonPositiveInteger
│   │   │   └── xsd:negativeInteger
│   │   └── xdd:integerRange
│   └── xdd:decimalRange
├── xsd:double
├── xsd:float
├── xsd:dateTime
│   └── xsd:dateTimeStamp
├── xsd:date
│   └── xdd:dateRange
├── xsd:time
├── xsd:duration
│   ├── xsd:yearMonthDuration
│   ├── xsd:dayTimeDuration
│   └── xdd:dateTimeInterval
├── xsd:gYear
│   └── xdd:gYearRange
├── xsd:gMonth
├── xsd:gDay
├── xsd:gYearMonth
├── xsd:gMonthDay
├── xsd:base64Binary
├── xsd:hexBinary
└── xsd:anyURI

rdfs:Literal
└── rdf:langString
    └── rdf:PlainLiteral

xdd:json (standalone)
xdd:coordinate (standalone)
xdd:coordinatePolygon (standalone)
xdd:coordinatePolyline (standalone)

sys:JSON (system type)
sys:JSONDocument (system type)
sys:Dictionary (system type)

XSD Core Types

xsd:string

The fundamental string type. All string-derived types can be cast to and from xsd:string.

Property	Value
IRI	`http://www.w3.org/2001/XMLSchema#string`
Parent	`xsd:anySimpleType`
JSON Representation	JSON string
Example	`"Hello, World!"`

xsd:boolean

Boolean true/false values.

Property	Value
IRI	`http://www.w3.org/2001/XMLSchema#boolean`
Parent	`xsd:anySimpleType`
Valid Values	`true`, `false`, `1`, `0`
JSON Representation	JSON boolean (`true` or `false`)
Typecasting	String `"true"` or `"1"` → `true`; `"false"` or `"0"` → `false`

xsd:decimal

Arbitrary-precision decimal numbers. TerminusDB stores these internally as rational numbers to preserve exact precision.

Property	Value
IRI	`http://www.w3.org/2001/XMLSchema#decimal`
Parent	`xsd:anySimpleType`
Internal Storage	Arbitrary-precision rationals
JSON Serialization	JSON number (20 significant digits)
String Serialization	Minimal form without trailing zeros (e.g., `33` → `"33"`)

Precision Notes:

Input values are parsed as exact rationals (e.g., 0.5679 → 5679/10000)
JSON output uses 20 significant digits for decimal representation
Round-trip conversion preserves exactness within precision limits

xsd:double

IEEE 754 double-precision (64-bit) floating-point numbers.

Property	Value
IRI	`http://www.w3.org/2001/XMLSchema#double`
Parent	`xsd:anySimpleType`
Internal Storage	IEEE 754 binary64
Special Values	`INF`, `-INF`, `NaN`
String Serialization	Always includes decimal point (e.g., `33` → `"33.0"`)

Important: xsd:double is not a subtype of xsd:decimal. They use different numeric representations.

xsd:float

IEEE 754 single-precision (32-bit) floating-point numbers.

Property	Value
IRI	`http://www.w3.org/2001/XMLSchema#float`
Parent	`xsd:anySimpleType`
Internal Storage	IEEE 754 binary32
Special Values	`INF`, `-INF`, `NaN`
String Serialization	Always includes decimal point (e.g., `33` → `"33.0"`)

Important: xsd:float is not a subtype of xsd:decimal. Like xsd:double, it uses IEEE 754 representation.

XSD Integer Types

All integer types derive from xsd:decimal → xsd:integer and use arbitrary-precision integers (GMP integers in Prolog).

xsd:integer

Arbitrary-precision signed integer with no range limits.

Property	Value
IRI	`http://www.w3.org/2001/XMLSchema#integer`
Parent	`xsd:decimal`
Range	Unlimited (arbitrary precision)
String Serialization	No decimal point (e.g., `33` → `"33"`)

Signed Integer Types

Type	Range	Parent
xsd:long	−9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 (64-bit)	`xsd:integer`
xsd:int	−2,147,483,648 to 2,147,483,647 (32-bit)	`xsd:long`
xsd:short	−32,768 to 32,767 (16-bit)	`xsd:int`
xsd:byte	−128 to 127 (8-bit)	`xsd:short`

Unsigned Integer Types

Type	Range	Parent
xsd:unsignedLong	0 to 18,446,744,073,709,551,615 (64-bit)	`xsd:nonNegativeInteger`
xsd:unsignedInt	0 to 4,294,967,295 (32-bit)	`xsd:unsignedLong`
xsd:unsignedShort	0 to 65,535 (16-bit)	`xsd:unsignedInt`
xsd:unsignedByte	0 to 255 (8-bit)	`xsd:unsignedShort`

Constrained Integer Types

Type	Constraint	Parent
xsd:positiveInteger	0	`xsd:nonNegativeInteger`
xsd:nonNegativeInteger	≥ 0	`xsd:integer`
xsd:negativeInteger	< 0	`xsd:nonPositiveInteger`
xsd:nonPositiveInteger	≤ 0	`xsd:integer`

Typecasting: Integer types validate range constraints during casting. Attempting to cast -1 to xsd:nonNegativeInteger throws a casting error.

XSD Date and Time Types

xsd:dateTime

Combined date and time with optional timezone.

Property	Value
IRI	`http://www.w3.org/2001/XMLSchema#dateTime`
Format	`YYYY-MM-DDTHH:MM:SS[.sss][Z\|±HH:MM]`
Example	`"2012-10-09T00:00:00Z"`
Internal	`date_time(Year, Month, Day, Hour, Minute, Second, Offset)`

xsd:dateTimeStamp

DateTime that requires a timezone. Interchangeable with xsd:dateTime in practice.

xsd:date

Calendar date without time component.

Property	Value
IRI	`http://www.w3.org/2001/XMLSchema#date`
Format	`YYYY-MM-DD[Z\|±HH:MM]`
Example	`"2023-12-25"`

xsd:time

Time of day without date component.

Property	Value
IRI	`http://www.w3.org/2001/XMLSchema#time`
Format	`HH:MM:SS[.sss][Z\|±HH:MM]`
Example	`"14:30:00Z"`

Duration Types

Type	Format	Example
xsd:duration	`PnYnMnDTnHnMnS`	`"P1Y2M3DT4H5M6S"`
xsd:yearMonthDuration	`PnYnM`	`"P1Y6M"`
xsd:dayTimeDuration	`PnDTnHnMnS`	`"P5DT3H"`

Gregorian Types

Type	Format	Example
xsd:gYear	`YYYY[Z\|±HH:MM]`	`"1990"`
xsd:gMonth	`--MM[Z\|±HH:MM]`	`"--12"`
xsd:gDay	`---DD[Z\|±HH:MM]`	`"---25"`
xsd:gYearMonth	`YYYY-MM[Z\|±HH:MM]`	`"2023-12"`
xsd:gMonthDay	`--MM-DD[Z\|±HH:MM]`	`"--12-25"`

Typecasting: xsd:dateTime can be cast to xsd:decimal to obtain a Unix timestamp.

XSD String-Derived Types

xsd:normalizedString

String with no carriage returns, line feeds, or tabs.

xsd:token

Normalized string with no leading/trailing whitespace and no consecutive spaces.

xsd:language

BCP 47 language tag (e.g., "en", "en-US", "fr-CA").

xsd:NMTOKEN

XML name token—letters, digits, hyphens, underscores, colons, and periods only.

xsd:Name

XML Name—must start with a letter or underscore.

xsd:NCName

Non-colonized Name—XML Name without colons.

XSD Binary Types

xsd:base64Binary

Base64-encoded binary data.

Property	Value
IRI	`http://www.w3.org/2001/XMLSchema#base64Binary`
Example	`"SGVsbG8gV29ybGQ="`

xsd:hexBinary

Hexadecimal-encoded binary data.

Property	Value
IRI	`http://www.w3.org/2001/XMLSchema#hexBinary`
Example	`"48656C6C6F"`

XSD URI Type

xsd:anyURI

URI reference (absolute or relative). Per XSD 1.1 spec and RFC 3987, accepts both absolute and relative URI references.

Property	Value
IRI	`http://www.w3.org/2001/XMLSchema#anyURI`
Valid Examples	`"http://example.com"`, `"../path/file.txt"`, `"#section"`, `"rdf:type"`

RDF Types

rdf:langString

String with an associated language tag.

Property	Value
IRI	`http://www.w3.org/1999/02/22-rdf-syntax-ns#langString`
Parent	`rdfs:Literal`
Example	`"Hello"@en`, `"Bonjour"@fr`

rdf:PlainLiteral

Plain literal that can be cast from xsd:string. Represented with an empty language tag internally.

rdf:XMLLiteral

XML content as a literal. Note: Not fully implemented.

XDD Extension Types

TerminusDB provides custom extension types under the xdd: namespace (http://terminusdb.com/schema/xdd#).

xdd:coordinate

Geographic coordinate as [longitude, latitude].

Property	Value
IRI	`http://terminusdb.com/schema/xdd#coordinate`
Format	`[longitude, latitude]`
Example	`[-122.4194, 37.7749]`

xdd:coordinatePolygon

Polygon defined as an array of coordinate arrays.

Property	Value
IRI	`http://terminusdb.com/schema/xdd#coordinatePolygon`
Format	`[[[lng, lat], [lng, lat], ...], ...]`
Example	`[[[-122.4, 37.7], [-122.5, 37.8], [-122.4, 37.8], [-122.4, 37.7]]]`

xdd:coordinatePolyline

Polyline defined as an array of coordinates.

Property	Value
IRI	`http://terminusdb.com/schema/xdd#coordinatePolyline`
Format	`[[lng, lat], [lng, lat], ...]`

xdd:json

Arbitrary JSON data stored as a dictionary/object.

Property	Value
IRI	`http://terminusdb.com/schema/xdd#json`
Typecasting	String containing valid JSON → `xdd:json` dictionary
Example	`{"key": "value", "count": 42}`

Typecasting from string: When casting from xsd:string, the string is parsed as JSON. Invalid JSON throws a casting error.

xdd:url

Validated URL (subtype of xsd:string). Can also be cast from xsd:anyURI.

Property	Value
IRI	`http://terminusdb.com/schema/xdd#url`
Parent	`xsd:string`
Example	`"https://terminusdb.com"`

xdd:email

Email address format validation.

Property	Value
IRI	`http://terminusdb.com/schema/xdd#email`
Parent	`xsd:string`
Example	`"user@example.com"`

xdd:html

HTML content as a string.

Property	Value
IRI	`http://terminusdb.com/schema/xdd#html`
Parent	`xsd:string`
Example	`"<p>Hello <strong>World</strong></p>"`

Range Types

Range types store a pair of values representing a range.

Type	Base Type	Format	Example
xdd:dateRange	`xsd:date`	`[startDate, endDate]`	`["2023-01-01", "2023-12-31"]`
xdd:gYearRange	`xsd:gYear`	`[startYear, endYear]`	`[1990, 2000]`
xdd:integerRange	`xsd:integer`	`[min, max]`	`[1, 100]`
xdd:decimalRange	`xsd:decimal`	`[min, max]`	`[0.0, 1.0]`

xdd:dateTimeInterval

ISO 8601 time interval with half-open semantics [start, end]. Inherits from xsd:duration and supports all four ISO 8601 interval forms. Designed for temporal algebra (Allen's Interval Algebra) and clean interval partitioning.

Property	Value
IRI	`http://terminusdb.com/schema/xdd#dateTimeInterval`
Parent	`xsd:duration`
Semantics	Half-open interval `[start, end]` — start is included, end is excluded
Forms	Start/end: `2025-01-01/2025-04-01`, Start/duration: `2025-01-01/P3M`, Duration/end: `P3M/2025-04-01`, Duration only: `P3M`
Example	`"2025-01-01/2025-04-01"`

Typecasting:

Direction	Behavior
`xsd:string → xdd:dateTimeInterval`	Parses ISO 8601 interval notation (all four forms)
`xdd:dateTimeInterval → xsd:string`	Formats to ISO 8601 interval notation
`xdd:dateRange → xdd:dateTimeInterval`	Converts inclusive end to exclusive by adding one day: `[Jan 1, Mar 31]` → `Jan 1/Apr 1`
`xdd:dateTimeInterval → xdd:dateRange`	Converts exclusive end to inclusive by subtracting one day: `Jan 1/Apr 1` → `[Jan 1, Mar 31]`
`xsd:duration → xdd:dateTimeInterval`	Wraps duration as a form-4 (duration-only) interval
`xdd:dateTimeInterval → xsd:duration`	Extracts the duration component from the interval

For detailed usage, see the Allen's Interval Algebra guide.

System Types

System types under the sys: namespace (http://terminusdb.com/schema/sys#) provide special handling for JSON and document data.

sys:JSON

Arbitrary JSON value that can be any JSON type (object, array, string, number, boolean, null).

Property	Value
IRI	`http://terminusdb.com/schema/sys#JSON`
Usage	Schema property type for arbitrary JSON
Example	`{"any": "json", "values": [1, 2, 3]}`

sys:JSONDocument

A complete JSON document stored as a top-level entity.

Property	Value
IRI	`http://terminusdb.com/schema/sys#JSONDocument`
Usage	Document class for JSON-only documents

sys:Dictionary

Internal dictionary/object type used for JSON handling.

Property	Value
IRI	`http://terminusdb.com/schema/sys#Dictionary`
Usage	Internal type for Prolog dictionary representation

For detailed information on using sys:JSON and sys:JSONDocument in schemas, see sys:JSON Reference.

Typecasting Rules

TerminusDB supports explicit typecasting between compatible types. The general rules are:

String Conversions

All types can typically be cast to and from xsd:string:

Direction	Behavior
To string	Value is serialized to its canonical string representation
From string	String is parsed and validated according to type constraints

Numeric Type Conversions

Source	Target	Rule
`xsd:decimal`	`xsd:integer`	Succeeds only if value is whole number
`xsd:double`/`xsd:float`	`xsd:decimal`	Converts IEEE 754 float to rational
`xsd:double`/`xsd:float`	`xsd:integer`	Succeeds only if value equals its floor
`xsd:integer` subtypes	Each other	Validates range constraints

String Serialization of Numeric Types

When casting numeric types to xsd:string:

Source Type	String Format	Example
`xsd:double`	Always with decimal point	`33` → `"33.0"`
`xsd:float`	Always with decimal point	`33` → `"33.0"`
`xsd:decimal`	Minimal form	`33` → `"33"`
`xsd:integer`	No decimal point	`33` → `"33"`

Type Subsumption

Child types can be used where parent types are expected. For example:

xsd:int values are valid xsd:long values
xdd:url values are valid xsd:string values

Reserved/Unimplemented Types

The following XSD types are defined but not implemented:

Type	Status
`xsd:NOTATION`	Unimplemented
`xsd:QName`	Unimplemented
`xsd:ID`	Unimplemented
`xsd:IDREF`	Unimplemented
`xsd:ENTITY`	Unimplemented