Pre-defined types

Most pre-defined types are defined in the XSD but the XDM and XPath specifications augment these with additional types, such as:

xs:dateTimeStamp
xs:error
xs:numeric
items types

For more detailed information about types, see:

Schemas and Types in the XDM 4.0 specification
Types in the XPath 4.0 specification
Atomic Items in the XDM 4.0 specification
Atomic Comparisons: An Overview (Non-Normative) in the XPath 4.0 specification

Table of pre-defined types

The table below is an attempt to create an alphabetical list of all the types, how they relate to each other and the categories they are formally or colloquially assigned to in the specification documents.

There are two main categories of pre-defined type: schema types (which are mostly prefixed with xs:) and item types (which are suffixed with a pair of round brackets). In the table below, additional categories are listed. These are classes of type defined in one or more the specifications; see abbreviations brackets.

From XPath 4.0, for the purpose of comparing atomic items, the primitive atomic types are divided into a number of comparison families: atomic items belonging to types in the same family are mutually comparable, items belonging to different type families are not.

Name	Description	Category	Parent type	Sub-types	Comparison family	Notes
`xs:anyAtomicType`	A generalisation, representing any atomic item type.	Schema (XSD, XDM) Special (XSD) Atomic Generalized Atomic (XPath) Abstract (XPath)	`xs:anySimpleType`	`xs:anyURI`, `xs:base64Binary`, `xs:boolean`, `xs:date`, `xs:dateTime`, `xs:decimal`, `xs:double`, `xs:duration`, `xs:float`, `xs:gDay`, `xs:gMonth`, `xs:gMonthDay`, `xs:gYear`, `xs:gYearMonth`, `xs:hexBinary`, `xs:NOTATION`, `xs:QName`, `xs:string`, `xs:time`, `xs:untypedAtomic`		Introduced in XDM 3.0. Sources: [1], [4], [10], [11], [13], [14]
`xs:anySimpleType`	A restriction of xs:anyType to just all atomic values and all finite-length lists of zero or more atomic values.	Schema (XSD) Special (XSD) Abstract (XPath)	`xs:anyType`	`xs:anyAtomicType`, `list`, `union`		Introduced in XDM 3.0. Sources: [1], [10], [13]
`xs:anyType`	A generalisation that represents all datatypes.	Schema (XSD) Ordinary Abstract (XPath)		`xs:anySimpleType`, `sequence`		Sources: [1], [6], [13]
`xs:anyURI`	An Internationalized Resource Identifier Reference (IRI).	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath)	`xs:anyAtomicType`		String-like	Sources: [1], [3], [4], [11], [14]
`array()`	An array.	Item (XPath)	`function()`		Function	For more information, see Arrays. Sources: [22]
`attribute()`	An XML attribute.	Item (XPath)	`node()`	`schema-attribute()`	Attribute	Sources: [22]
`xs:base64Binary`	Arbitrary Base64-encoded binary data.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath)	`xs:anyAtomicType`		Binary	Sources: [1], [3], [4], [11], [14]
`xs:boolean`	The values `true` or `false`.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath)	`xs:anyAtomicType`		Boolean	Sources: [1], [3], [4], [11], [14]
`xs:byte`	A generalized atomic type.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:short`		Numeric	Sources: [1], [4], [6], [14]
`comment()`	An XML comment.	Item (XPath)	`node()`		Comment	Sources: [22]
`xs:date`	An entire calendar day.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath) date/time	`xs:anyAtomicType`		Date	Sources: [1], [3], [4], [11], [14]
`xs:dateTime`	An instant in time.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath) date/time	`xs:anyAtomicType`	`xs:dateTimeStamp`	DateTime	Sources: [1], [3], [4], [11], [14]
`xs:dateTimeStamp`	A generalized atomic type.	Schema (XSD, XDM) Atomic Ordinary Generalized Atomic (XPath) date/time	`xs:dateTime`		DateTime	Sources: [1], [4], [6], [11], [14]
`xs:dayTimeDuration`	A generalized atomic type.	Schema (XSD, XDM) Atomic Generalized Atomic (XPath) Ordinary date/time	`xs:duration`		Duration	Introduced in XDM 3.0. Sources: [1], [4], [6], [11], [14]
`xs:decimal`	A real number that can be represented by decimal numerals.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath)	`xs:anyAtomicType`	`xs:integer`	Numeric	Sources: [1], [3], [4], [11], [14]
`document-node()`	A wrapper node that represents an XML document.	Item (XPath)	`node()`		Document	Sources: [22]
`xs:double`	A double-precision floating point number.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath)	`xs:anyAtomicType`		Numeric	Sources: [1], [3], [4], [11], [14]
`xs:duration`	A duration of time without fixed endpoints.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath) date/time	`xs:anyAtomicType`	`xs:dayTimeDuration`, `xs:yearMonthDuration`	Duration	Sources: [1], [3], [4], [11], [14]
`element()`	An XML element.	Item (XPath)	`node()`	`schema-element()`	Element	Sources: [22]
`empty-sequence()`		Special (XPath)	`sequence`			Sources: [24]
`xs:ENTITIES`	A list of `xs:ENTITY` values.	Schema (XSD, XDM) List Ordinary	`list`			See Types adopted from XML Schema Sources: [1], [5], [6], [11]
`xs:ENTITY`	An XML entity.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:NCName`		String-like	Sources: [1], [4], [6], [12], [14]
`enum()`	A constraint on `xs:string`, restricting the set of valid values.	Item (XPath) Generalized Atomic (XPath)	`item()`		N/A	Sources: [14], [19], [22]
`xs:error`	A union type. Also a generalized atomic type.	Schema (XDM) Union Generalized Atomic (XPath)	`union`			Not expected to have any instances. See Types adopted from XML Schema Sources: [7], [11], [14]
`xs:float`	A floating point number.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath)	`xs:anyAtomicType`		Numeric	Sources: [1], [3], [4], [11], [14]
`function()`	A function.	Item (XPath)	`item()`	`array()`, `map()`	Function	For more information, see Function items. From XPath 4.0, function items have an identity property, which can be used to test whether two variables refer to the same function item or not. Sources: [22]
`xs:gDay`	A whole Gregorian day within an arbitrary month and year.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath) date/time	`xs:anyAtomicType`		gDay	Sources: [1], [3], [4], [11], [14]
`xs:gMonth`	A whole Gregorian month within an arbitrary year.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath) date/time	`xs:anyAtomicType`		gMonth	Sources: [1], [3], [4], [11], [14]
`xs:gMonthDay`	A whole day within a specific Gregorian month in an arbitrary year.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath) date/time	`xs:anyAtomicType`		gMonthDay	Sources: [1], [3], [4], [11], [14]
`gnode()`	A generalized node. It is always either an `xnode()` or a `jnode()`.	Item (XPath) Abstract (XPath)	`item()`	`jnode()`, `node()`		Introduced in XDM 4.0. Sources: [13], [15], [22]
`xs:gYear`	A whole Gregoria year.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath) date/time	`xs:anyAtomicType`		gYear	Sources: [1], [3], [4], [11], [14]
`xs:gYearMonth`	A whole Gregorian month in a specific Gregorian year.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath) date/time	`xs:anyAtomicType`		gYearMonth	Sources: [1], [3], [4], [11], [14]
`xs:hexBinary`	Arbitrary hex-encoded binary data.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath)	`xs:anyAtomicType`		Binary	Sources: [1], [3], [4], [11], [14]
`xs:ID`	An XML identifier.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:NCName`		String-like	Sources: [1], [4], [6], [8], [12], [14]
`xs:IDREF`	A cross-reference to an `xs:ID`.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:NCName`		String-like	Sources: [1], [4], [6], [12], [14]
`xs:IDREFS`	A list of `xs:IDREF` values.	Schema (XSD, XDM) List Ordinary	`list`			See Types adopted from XML Schema Sources: [1], [5], [6], [11]
`xs:int`	A generalized atomic type.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:long`	`xs:short`	Numeric	Sources: [1], [4], [6], [14]
`xs:integer`	A generalized atomic type.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:decimal`	`xs:long`, `xs:nonNegativeInteger`, `xs:nonPositiveInteger`	Numeric	Sources: [1], [4], [6], [14]
`item()`	An item is either an atomic item, a GNode, or a function item.	Item (XPath)	`sequence`	`function()`, `gnode()`, `enum()`		Sources: [16], [22]
`jnode()`	An encapsulation of a value as it appears within a tree of maps and arrays, typically (but not necessarily) obtained by parsing JSON texts.	Item (XPath)	`gnode()`		JNode	Introduced in XDM 4.0. Sources: [17], [22]
`xs:language`	A formal natural language identifier.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:token`		String-like	Sources: [1], [4], [6], [9], [12], [14]
`list`		Abstract (XSD)	`xs:anySimpleType`	`xs:ENTITIES`, `xs:IDREFS`, `xs:NMTOKENS`		Sources: [2], [5]
`xs:long`	A generalized atomic type.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:integer`	`xs:int`	Numeric	Sources: [1], [4], [6], [14]
`map()`	A map.	Item (XPath)	`function()`	`record()`	Function	For more information, see Maps. A `record()` may be used to constrain the type of items that may be added to a map. Sources: [22]
`xs:Name`	An XML Name.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:token`	`xs:NCName`	String-like	Sources: [1], [4], [6], [12], [14]
`namespace-node()`	An XML namespace node.	Item (XPath)	`node()`		Namespace	Sources: [22]
`xs:NCName`	An XML "non-colonized" `xs:Name`	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:Name`	`xs:ID`, `xs:IDREF`, `xs:ENTITY`	String-like	Sources: [1], [4], [6], [12], [14]
`xs:negativeInteger`	A generalized atomic type.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:nonPositiveInteger`		Numeric	Sources: [1], [4], [6], [14]
`xs:NMTOKEN`	A single name token.	Schema (XSD) Ordinary Atomic Generalized Atomic (XPath)	`xs:token`		String-like	Sources: [1], [4], [6], [12], [14]
`xs:NMTOKENS`	A list of `xs:NMTOKEN` values.	Schema (XSD, XDM) Ordinary List	`list`			Sources: [1], [5], [6], [11]
`node()`	An XML node. Also known as: `xnode()`	Item (XPath)	`gnode()`	`attribute()`, `comment()`, `document-node()`, `element()`, `namespace-node()`, `processing-instruction()`, `text()`	XNode	While the concept of a node existed before 4.0, the term `xnode()` was introduced in 4.0 to differentiate between XML nodes and JSON nodes (see `jnode()`). Sources: [18], [22]
`xs:nonNegativeInteger`	A generalized atomic type.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:integer`	`xs:positiveInteger`	Numeric	Sources: [1], [4], [6], [14]
`xs:nonPositiveInteger`	A generalized atomic type.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:integer`	`xs:negativeInteger`	Numeric	Sources: [1], [4], [6], [14]
`xs:normalizedString`	A string that doesn't contain the following characters: carriage return (`#xD`); line feed (`#xA`); line feed (`#x9`).	Schema (XSD) Ordinary Atomic Generalized Atomic (XPath)	`xs:string`	`xs:token`	String-like	Sources: [1], [4], [6], [14]
`xs:NOTATION`	An XML notation attribute.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath) Namespace-sensitive (XPath) Abstract (XPath)	`xs:anyAtomicType`		Notation	Sources: [1], [3], [4], [11], [13], [14], [23]
`xs:numeric`	A union type whose members are: `xs:double`, `xs:float` and `xs:decimal`.	Schema (XDM) Union Generalized Atomic (XPath)	`union`			See Types adopted from XML Schema Sources: [7], [11], [14]
`xs:positiveInteger`	A generalized atomic type.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:nonNegativeInteger`	`xs:unsignedLong`	Numeric	Sources: [1], [4], [6], [14]
`processing-instruction()`	A processing instruction (PI).	Item (XPath)	`node()`		Processing-instruction	Sources: [22]
`xs:QName`	An XML qualified name.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath) Namespace-sensitive (XPath)	`xs:anyAtomicType`		QName	Sources: [1], [3], [4], [11], [14], [23]
`record()`	May be used to constrain the type of items that may be added to a map.	Item (XPath)	`map()`		Function	Sources: [22]
`schema-attribute()`	A schema attribute.	Item (XPath)	`attribute()`		Schema Attribute	While the concept of a `schema-attribute()` existed before 4.0, XPath 4.0 classifies it as a sub-type of `attribute()`. Sources: [20], [22]
`schema-element()`	A schema element.	Item (XPath)	`element()`		Schema Element	While the concept of a `schema-element()` existed before 4.0, XPath 4.0 classifies it as a sub-type of `element()`. Sources: [21], [22]
`sequence`	One or more occurrences of an `empty-sequence()`, `item()` or non-abstract sub-type of `xs:anyAtomicType`.	Abstract (XPath)	`xs:anyType`	`empty-sequence()`, `item()`		Sources: [13]
`xs:short`	An `xs:int` between -32768 and 32767 (inclusive).	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary Numeric	`xs:int`	`xs:byte`		Sources: [1], [4], [6], [14]
`xs:string`	A string of characters.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath)	`xs:anyAtomicType`	`xs:normalizedString`	String-like	Sources: [1], [3], [4], [11], [14]
`text()`	Text in XML.	Item (XPath)	`node()`		Text	Sources: [22]
`xs:time`	An instant in time that recurs at the same point in each calendar day, or that occurs in some arbitrary calendar day.	Schema (XSD, XDM) Primitive Atomic Generalized Atomic (XPath)	`xs:anyAtomicType`		Time	Sources: [1], [3], [4], [11], [14]
`xs:token`	An xs:normalizedString that has no leading or trailing spaces (`#x20`) and includes no internal sequences of two or more spaces.	Schema (XSD) Ordinary Atomic Generalized Atomic (XPath)	`xs:normalizedString`	`xs:NMTOKEN`, `xs:language`, `xs:Name`	String-like	Sources: [1], [4], [6], [12], [14]
`union`	A generalized type.	Abstract (XSD)	`xs:anySimpleType`	`xs:error`, `xs:numeric`	N/A	Sources: [2]
`xs:unsignedByte`	Derived from `xs:unsignedShort` by setting the value of maxInclusive to 255.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:unsignedShort`		Numeric	Sources: [1], [4], [6], [14]
`xs:unsignedInt`	Derived from `xs:unsignedLong` by setting the value of maxInclusive to 4294967295.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:unsignedLong`	`xs:unsignedShort`	Numeric	Sources: [1], [4], [6], [14]
`xs:unsignedLong`	A generalized atomic type.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:positiveInteger`	`xs:unsignedInt`	Numeric	Sources: [1], [4], [6], [14]
`xs:unsignedShort`	Derived from `xs:unsignedInt` by setting the value of maxInclusive to 65535.	Schema (XSD) Atomic Generalized Atomic (XPath) Ordinary	`xs:unsignedInt`	`xs:unsignedByte`	Numeric	Sources: [1], [4], [6], [14]
`xs:untypedAtomic`	A primitive atomic type.	Schema (XSD, XDM) Atomic Generalized Atomic (XPath) Ordinary	`xs:anyAtomicType`		String-like	Sources: [1], [4], [6], [11], [14]
`xnode()`	An alternative name for `node()`.					Introduced in XDM 4.0. This alternative name is only used in documentation. It's not expected to be used in code.
`xs:yearMonthDuration`	A generalized atomic type.	Schema (XSD, XDM) Atomic Generalized Atomic (XPath) Ordinary date/time	`xs:duration`		Duration	Introduced in XDM 3.0. Sources: [1], [4], [6], [11], [14]

Sources