XPath and XQuery Functions and Operators 4.0

17 External resources and data formats

These functions in this section access resources external to a query or stylesheet, and convert between external file formats and their XPath and XQuery data model representation.

17.4 Functions on JSON Data

The functions listed in this section parse or serialize JSON data.

JSON is a popular format for exchange of structured data on the web: it is specified in [RFC 7159]. This section describes facilities allowing JSON data to be converted to and from XDM values.

This specification describes two ways of representing JSON data losslessly using XDM constructs. The first method uses XDM maps to represent JSON objects, and XDM arrays to represent JSON arrays. The second method represents all JSON constructs using XDM element and attribute nodes.

Function	Meaning
`fn:parse-json`	Parses input supplied in the form of a JSON text, returning the results typically in the form of a map or array.
`fn:json-doc`	Reads an external resource containing JSON, and returns the result of parsing the resource as JSON.
`fn:json-to-xml`	Parses a string supplied in the form of a JSON text, returning the results in the form of an XML document node.
`fn:xml-to-json`	Converts an XML tree, whose format corresponds to the XML representation of JSON defined in this specification, into a string conforming to the JSON grammar.

Note also:

The function fn:serialize has an option to generate JSON output from a structure of maps and arrays.
The function fn:element-to-map enables arbitrary XML node trees to be converted to trees of maps and arrays suitable for serializing as JSON.

17.4.4 fn:parse-json

Changes in 4.0 (next | previous)

The rules regarding use of non-XML characters in JSON texts have been relaxed. [Issue 414 PR 546 25 July 2023]
An option is provided to control how the JSON null value should be handled. [Issue 960 PR 1028 20 February 2024]
An option is provided to control how JSON numbers should be formatted. [Issues 973 1037 PRs 975 1058 1246 12 March 2024]
It is now recommended that out-of-range xs:double values should translate to positive or negative infinity. [Issue 641 PR 2387 16 January 2026]
It is now recommended that out-of-range xs:double values should translate to positive or negative infinity. [Issue 641 PR 2387 16 January 2026]
The default for the escape option has been changed to false. The 3.1 specification gave the default value as true, but this appears to have been an error, since it was inconsistent with examples given in the specification and with tests in the test suite. [Issue 1555 PR 1565 11 November 2024]
The order of entries in maps is retained. [Issue 1651 PR 1703 14 January 2025]

Summary

Parses input supplied in the form of a JSON text, returning the results typically in the form of a map or array.

Signature

`fn:parse-json`(
`$value`	`as` `xs:string?`,
`$options`	`as` `map(*)?`	`:=` `{}`
) `as` `item()?`

Properties

This function is deterministic, context-independent, and focus-independent.

Rules

If the second argument is omitted or an empty sequence, the result is the same as calling the two-argument form with an empty map as the value of the $options argument.

The first argument is a JSON text as defined in [RFC 7159], in the form of a string or binary value. The function parses this input to return an XDM value.

If $value is the empty sequence, the function returns the empty sequence.

Note:

If the input is "null", the result will also be an empty sequence.

The $options argument can be used to control the way in which the parsing takes place. The option parameter conventions apply.

The entries that may appear in the $options map are as follows:

`record(`
`liberal?`	`as` `xs:boolean`,
`duplicates?`	`as` `xs:string`,
`escape?`	`as` `xs:boolean`,
`fallback?`	`as` `(fn(xs:string) as xs:anyAtomicType)?`,
`null?`	`as` `item()*`,
`number-parser?`	`as` `(fn(xs:untypedAtomic) as item()?)?`
`)`

Key	Value	Meaning
`liberal?`	Determines whether deviations from the syntax of RFC7159 are permitted. Type: `xs:boolean` Default: `false`
	`false`	The input must consist of an optional byte order mark (which is ignored) followed by a string that conforms to the grammar of `JSON-text` in [RFC 7159]. An error must be raised [err:FOJS0001] if the input does not conform to the grammar.
	`true`	The input may contain deviations from the grammar of [RFC 7159], which are handled in an implementation-defined way. (Note: some popular extensions include allowing quotes on keys to be omitted, allowing a comma to appear after the last item in an array, allowing leading zeroes in numbers, and allowing control characters such as tab and newline to be present in unescaped form.) Since the extensions accepted are implementation-defined, an error may be raised [err:FOJS0001] if the input does not conform to the grammar.
`duplicates?`	Determines the policy for handling duplicate keys in a JSON object. To determine whether keys are duplicates, they are compared using the Unicode codepoint collation, after expanding escape sequences, unless the `escape` option is set to `true`, in which case keys are compared in escaped form. Type: `xs:string` Default: `use-first`
	`reject`	An error is raised [err:FOJS0003] if duplicate keys are encountered.
	`use-first`	If duplicate keys are present in a JSON object, all but the first of a set of duplicates are ignored.
	`use-last`	If duplicate keys are present in a JSON object, all but the last of a set of duplicates are ignored.
`escape?`	Determines whether special characters are represented in the XDM output in backslash-escaped form. Type: `xs:boolean` Default: `false`
	`false`	Any permitted character in the input, whether or not it is represented in the input by means of an escape sequence, is represented as an unescaped character in the result. Any other character or codepoint (for example, an unpaired surrogate) is passed to the `fallback` function as described below; in the absence of a fallback function, it is replaced by U+FFFD (REPLACEMENT CHARACTER, `�`) .
	`true`	JSON escape sequences are used in the result to represent special characters in the JSON input, as defined below, whether or not they were represented using JSON escape sequences in the input. The characters that are considered “special” for this purpose are: all codepoints in the range U+0000 (NULL) to U+001F (IS1) or U+007F (DELETE) to U+009F (APC) ; all codepoints that do not represent permitted characters, including codepoints representing unpaired surrogates; the character U+005C (REVERSE SOLIDUS, BACKSLASH, `\`) itself. Such characters are represented using a two-character escape sequence where available (for example, `\t`), or a six-character escape sequence otherwise (for example `\uDEAD`). Characters other than these are not escaped in the result, even if they were escaped in the input.
`fallback?`	Provides a function which is called when the input contains an escape sequence that represents a character that is not a permitted character. It is an error to supply the `fallback` option if the `escape` option is present with the value `true`. Type: `(fn(xs:string) as xs:anyAtomicType)?` Default: `fn { char(0xFFFD) }`
`fallback?`	`User-supplied function`	The function is called when the JSON input contains character that is not a permitted character It is called once for any surrogate that is not properly paired with another surrogate. The untyped atomic item supplied as the argument will always be a two- or six-character escape sequence, starting with a backslash, that conforms to the rules in the JSON grammar (as extended by the implementation if `liberal:true()` is specified): for example `\b` or `\uFFFF` or `\uDEAD`. By default, the escape sequence is replaced with the Unicode `REPLACEMENT CHARACTER`. The function is not called for an escape sequence that is invalid against the grammar (for example `\x0A`). The string, which results from invoking `fn:string` on the result of the function, is inserted into the result in place of the invalid character. The function also has the option of raising a dynamic error by calling `fn:error`.
`null?`	Determines how the JSON `null` value should be represented. Type: `item()` Default:* `()`
`null?`	`Value`	The supplied XDM value is used to represent the JSON `null` value. The default representation of `null` is an empty sequence, which works well in cases where setting a property of an object to `null` has the same meaning as omitting the property. It works less well in cases where `null` is used with some other meaning, because expressions such as the lookup operator `?` flatten the result to a single sequence of items, which means that any entries whose value is an empty sequence effectively disappear. The property can be set to any XDM value; a suggested value is the `xs:QName` value `fn:QName("http://www.w3.org/2005/xpath-functions", "null")`, which is recognized by the JSON serialization method as representing the JSON value `null`.
`number-parser?`	Determines how numeric values should be processed. Type: `(fn(xs:untypedAtomic) as item()?)?` Default: `xs:double#1`
`number-parser?`	`User-supplied function`	The supplied function is called to process the string value of any JSON number in the input. By default, numbers are processed by converting to `xs:double` using the XPath casting rules. Supplying the value `xs:decimal#1` will instead convert to `xs:decimal` (which potentially retains more precision, but disallows exponential notation), while supplying a function that casts to `(xs:decimal \| xs:double)` will treat the value as `xs:decimal` if there is no exponent, or as `xs:double` otherwise. Supplying the value `fn:identity#1` causes the value to be retained unchanged as an `xs:untypedAtomic`. If the `liberal` option is `false` (the default), then the supplied `number-parser` is called if and only if the value conforms to the JSON grammar for numbers (for example, a leading plus sign and redundant leading zeroes are not allowed). If the `liberal` option is `true` then it is also called if the value conforms to an implementation-defined extension of this grammar.

The various structures that can occur in JSON are transformed recursively to XDM values as follows:

A JSON object is converted to a map. The entries in the map correspond to the key/value pairs in the JSON object. The key is always of type xs:string; the associated value may be of any type, and is the result of converting the JSON value by recursive application of these rules. For example, the JSON text { "x": 2, "y": 5 } is transformed to the value { "x": 2, "y": 5 }.
If duplicate keys are encountered in a JSON object, they are handled as determined by the duplicates option defined above.
The order of entries is retained.
A JSON array is transformed to an array whose members are the result of converting the corresponding member of the array by recursive application of these rules. For example, the JSON text [ "a", "b", null ] is transformed (by default) to the value [ "a", "b", () ].
A JSON string is converted to an xs:string value. The handling of special characters depends on the escape and fallback options, as described in the table above.
A JSON number is processed using the function supplied in the number-parser option; by default it is converted to an xs:double value using the rules for casting from xs:string to xs:double.
Note:
The casting rules leave implementations some flexibility as to how values should be handled when they are too large to represent as an xs:double. It is recommended that when parsing JSON, out-of-range values should be converted to positive or negative infinity. This option enables round-tripping behavior, since the JSON serialization method represents positive and negative infinity as 1e9999 or -1e9999 respectively.
Note:
Round-tripping of NaN can be achieved by setting the option "null": number("NaN")
The JSON boolean values true and false are converted to the corresponding xs:boolean values.
The JSON value null is converted to the value given by the null option, which defaults to an empty sequence.

Error Conditions

A dynamic error [err:FOJS0001] occurs if the value of $value does not conform to the JSON grammar, unless the option "liberal":true() is present and the processor chooses to accept the deviation.

A dynamic error [err:FOJS0003] occurs if the option "duplicates": "reject" is present and the value of $value contains a JSON object with duplicate keys.

A dynamic error [err:FOJS0005] occurs if the $options map contains an entry whose key is defined in this specification and whose value is not valid for that key, or if it contains an entry with the key fallback when the option "escape":true() is also present.

Notes

The result of the function will be an instance of one of the following types. An instance of test (or in XQuery, typeswitch) can be used to distinguish them:

map(xs:string, item()?) for a JSON object
array(item()?) for a JSON array
xs:string for a JSON string
xs:double for a JSON number
xs:boolean for a JSON boolean
empty-sequence() for a JSON null (or for empty input)

If the source of the JSON input is a resource accessible by URI, then it may be preferable to use the fn:json-doc function. If the source is a binary value (xs:hexBinary or xs:base64Binary) then this can first be decoded as a string using the functions bin:infer-encoding and bin:decode-string.

If the input starts with a byte order mark, this function ignores it. The byte order mark may have been added to the data stream in order to facilitate decoding of an octet stream to a character string, but since this function takes a character string as input, the byte order mark serves no useful purpose.

The possibility of the input containing characters that are not valid in XML (for example, unpaired surrogates) arises only when such characters are expressed using JSON escape sequences. This is because the input to the function is an instance of xs:string, which by definition (see [XQuery and XPath Data Model (XDM) 4.0] section 4.1.5 XML and XSD Versions) cannot contain unpaired surrogates.

The serializer provides an option to output data in json-lines format. This is a format for structured data containing one JSON value (usually but not necessarily a JSON object) on each line. There is no corresponding option to parse json-lines input, but this can be achieved using the expression unparsed-text-lines($uri) =!> parse-json().

Examples

Expression:	`parse-json('{ "x": 1, "y": [ 3, 4, 5 ] }')`
Result:	`{ "x": 1e0, "y": [ 3e0, 4e0, 5e0 ] }`
Expression:	`parse-json('"abcd"')`
Result:	`"abcd"`
Expression:	`parse-json('{ "x": "\\", "y": "\u0025" }')`
Result:	`{ "x": "\", "y": "%" }`
Expression:	parse-json( '{ "x": "\\", "y": "\u0025" }', { 'escape': true() } )
Result:	{ "x": "\\", "y": "%" }
Expression:	parse-json( '{ "x": "\\", "y": "\u0000" }' )
Result:	{ "x": "\", "y": char(0xFFFD) }
Expression:	parse-json( '{ "x": "\\", "y": "\u0000" }', { 'escape': true() } )
Result:	{ "x": "\\", "y": "\u0000" }
Expression:	parse-json( '{ "x": "\\", "y": "\u0000" }', { 'fallback': fn($s) { '[' \|\| $s \|\| ']' } } )
Result:	{ "x": "\", "y": "[\u0000]" }
Expression:	parse-json( "1984.2", { 'number-parser': fn { xs:integer(round(.)) } } )
Result:	1984
Expression:	parse-json( '[ 1, -1, 2 ]', { 'number-parser': fn { boolean(. >= 0) } } )
Result:	[ true(), false(), true() ]
Expression:	parse-json('[ "a", null, "b" ]', { 'null': #fn:null } )
Result:	[ "a", #fn:null, "b" ]

H Changes since 3.1 (Non-Normative)

H.1 Summary of Changes

If a section of this specification has been updated since version 3.1, an overview of the changes is provided, along with links to navigate to the next or previous change.
See 1 Introduction
Sections with significant changes are marked with a ✭ symbol in the table of contents. New functions are indicated by ✚.
See 1 Introduction
PR 1504 2329
New in 4.0
See 2.1.7 fn:insert-separator
New in 4.0
See 2.1.10 fn:replicate
New in 4.0
See 2.1.12 fn:slice
PR 1120 1150
A callback function can be supplied for comparing individual items.
See 2.2.4 fn:deep-equal
Changed in 4.0 to use transitive equality comparisons for numeric values.
See 2.2.5 fn:distinct-values
PR 614 987
New in 4.0
See 2.2.6 fn:duplicate-values
New in 4.0. Originally proposed under the name fn:uniform
See 2.4.2 fn:all-equal
New in 4.0. Originally proposed under the name fn:unique
See 2.4.3 fn:all-different
New in 4.0
See 2.5.3 fn:every
New in 4.0
See 2.5.9 fn:highest
New in 4.0
See 2.5.10 fn:index-where
New in 4.0
See 2.5.11 fn:lowest
New in 4.0
See 2.5.15 fn:scan-right
New in 4.0
See 2.5.16 fn:some
PR 795 2228
New in 4.0
See 2.5.19 fn:sort-with
PR 521 761
New in 4.0
See 2.5.22 fn:transitive-closure
New in 4.0
See 4.4.5 fn:is-NaN
PR 1260 1275
A third argument has been added, providing control over the rounding mode.
See 4.4.6 fn:round
PR 1049 1151
Decimal format parameters can now be supplied directly as a map in the third argument, rather than referencing a format defined in the static context.
See 4.7.2 fn:format-number
PR 1205 1230
New in 4.0
See 4.8.2 math:e
See 4.8.8 math:cosh
See 4.8.15 math:sinh
See 4.8.18 math:tanh
The 3.1 specification suggested that every value in the result range should have the same chance of being chosen. This has been corrected to say that the distribution should be arithmetically uniform (because there are as many xs:double values between 0.01 and 0.1 as there are between 0.1 and 1.0).
See 4.9.2 fn:random-number-generator
PR 261 306 993
New in 4.0
See 5.4.1 fn:char
New in 4.0
See 5.4.2 fn:characters
PR 937 995 1190
New in 4.0
See 5.4.13 fn:hash
PR 215 415
New in 4.0
See 7.6.2 fn:parse-uri
PR 1423 1413
New in 4.0
See 7.6.3 fn:build-uri
New in 4.0
See 12.2.2 fn:in-scope-namespaces
PR 1620 1886
Options are added to customize the form of the output.
See 12.2.9 fn:path
PR 1547 1551
New in 4.0
See 12.2.11 fn:siblings
PR 969 1134
New in 4.0
See 14.4.6 map:filter
PR 478 515
New in 4.0
See 14.4.12 map:keys-where
PR 1575 1906
A new function fn:element-to-map is provided for converting XDM trees to maps suitable for serialization as JSON. Unlike the fn:xml-to-json function retained from 3.1, this can handle arbitrary XML as input.
See 14.5 Converting elements to maps
New in 4.0
See 15.2.3 array:empty
PR 968 1295
New in 4.0
See 15.2.13 array:index-of
PR 476 1087
New in 4.0
See 15.2.16 array:items
PR 360 476
New in 4.0
See 15.2.18 array:members
See 15.2.19 array:of-members
Supplying an empty sequence as the value of an optional argument is equivalent to omitting the argument.
See 15.2.29 array:subarray
PR 1117 1279
The $options parameter has been added.
See 17.1.6 fn:unparsed-text-lines
PR 259 956
A new function is available for processing input data in HTML format.
See 17.3 Functions on HTML Data
New in 4.0
See 17.3.2 fn:parse-html
PR 975 1058 1246
An option is provided to control how JSON numbers should be formatted.
See 17.4.4 fn:parse-json
Additional options are available, as defined by fn:parse-json.
See 17.4.5 fn:json-doc
PR 533 719 834 1066
New in 4.0
See 17.5.4 fn:csv-to-arrays
See 17.5.7 fn:parse-csv
PR 533 719 834 1066 1605
New in 4.0
See 17.5.10 fn:csv-to-xml
PR 791 1256 1282 1405
New in 4.0
See 17.6.1 fn:invisible-xml
PR 629 803
New in 4.0
See 21.2.2 fn:message
PR 533 719 834
New functions are available for processing input data in CSV (comma separated values) format.
See 17.5 Functions on CSV Data
Comparison of mixed numeric types (for example xs:double and xs:decimal) now generally converts both values to xs:decimal.
See 4.3 Comparing numeric values
PR 289 1901
A third argument is added, allowing user control of how absent keys should be handled.
See 14.4.9 map:get
A third argument is added, allowing user control of how index-out-of-bounds conditions should be handled.
See 15.2.11 array:get
A new collation URI is defined for Unicode case-insensitive comparison and ordering.
See 5.3.5 The Unicode case-insensitive collation
PR 1727 1740
It is no longer guaranteed that the new key replaces the existing key.
See 14.4.14 map:put
PR 173
New in 4.0
See 18.4 fn:op
PR 203
New in 4.0
See 14.4.1 map:build
PR 207
New in 4.0
See 10.1.2 fn:parse-QName
See 10.2.5 fn:expanded-QName
PR 222
New in 4.0
See 2.2.3 fn:contains-subsequence
See 2.2.7 fn:ends-with-subsequence
See 2.2.9 fn:starts-with-subsequence
PR 250
New in 4.0
See 2.1.3 fn:foot
See 2.1.15 fn:trunk
See 15.2.2 array:build
See 15.2.8 array:foot
See 15.2.31 array:trunk
PR 258
New in 4.0
See 15.2.14 array:index-where
PR 313
The second argument can now be a sequence of integers.
See 2.1.9 fn:remove
PR 319
New in 4.0. The function replaces the internal op:same-key function in 3.1
See 2.2.1 fn:atomic-equal
PR 326
Higher-order functions are no longer an optional feature.
See 1.2 Conformance
PR 360
New in 4.0
See 14.4.4 map:entries
PR 419
New in 4.0
See 2.1.8 fn:items-at
PR 434
New in 4.0
See 4.5.2 fn:parse-integer
The function has been extended to allow output in a radix other than 10, for example in hexadecimal.
See 4.6.1 fn:format-integer
PR 477
New in 4.0
See 15.2.24 array:slice
PR 482
Deleted an inaccurate statement concerning the behavior of NaN.
See 4.3 Comparing numeric values
PR 507
New in 4.0
See 2.5.13 fn:partition
PR 546
It is no longer automatically an error if the input contains a codepoint that is not valid in XML. Instead, the codepoint must be a permitted character. The set of permitted characters is implementation-defined, but it is recommended that all Unicode characters should be accepted.
See 5.2.1 fn:codepoints-to-string
It is no longer automatically an error if the resource (after decoding) contains a codepoint that is not valid in XML. Instead, the codepoint must be a permitted character. The set of permitted characters is implementation-defined, but it is recommended that all Unicode characters should be accepted.
See 17.1.5 fn:unparsed-text
The rules regarding use of non-XML characters in JSON texts have been relaxed.
See 17.4.3 JSON character repertoire
See 17.4.4 fn:parse-json
It is no longer automatically an error if the input contains a codepoint that is not valid in XML. Instead, the codepoint must be a permitted character. The set of permitted characters is implementation-defined, but it is recommended that all Unicode characters should be accepted.
See 17.4.5 fn:json-doc
PR 609
New in 4.0
See 15.2.28 array:split
PR 631
New in 4.0
See 7.1 fn:decode-from-uri
PR 662
Constructor functions now have a zero-arity form; the first argument defaults to the context item.
See 22 Constructor functions
PR 680
The case-insensitive collation is now defined normatively within this specification, rather than by reference to the HTML "living specification", which is subject to change. The collation can now be used for ordering comparisons as well as equality comparisons.
See 5.3.6 The HTML ASCII Case-Insensitive Collation
PR 702
The function can now take any number of arguments (previously it had to be two or more), and the arguments can be sequences of strings rather than single strings.
See 5.4.4 fn:concat
PR 710
Changes the function to return a sequence of key-value pairs rather than a map.
See 13.5 fn:function-annotations
PR 727
It has been clarified that loading a module has no effect on the static or dynamic context of the caller.
See 18.2 fn:load-xquery-module
PR 828
The $predicate callback function accepts an optional position argument.
See 2.5.4 fn:filter
The $action callback function accepts an optional position argument.
See 2.5.7 fn:for-each
See 2.5.8 fn:for-each-pair
The $predicate callback function now accepts an optional position argument.
See 15.2.4 array:filter
The $action callback function now accepts an optional position argument.
See 15.2.9 array:for-each
See 15.2.10 array:for-each-pair
PR 881
The way that fn:min and fn:max compare numeric values of different types has changed. The most noticeable effect is that when these functions are applied to a sequence of xs:integer or xs:decimal values, the result is an xs:integer or xs:decimal, rather than the result of converting this to an xs:float or xs:double.
See 2.4.5 fn:max
See 2.4.6 fn:min
PR 901
The optional third argument can now be supplied as an empty sequence.
See 2.1.13 fn:subsequence
The third argument can now be supplied as an empty sequence.
See 5.4.6 fn:substring
The second argument can now be an empty sequence.
See 6.3.3 fn:tokenize
The optional second argument can now be supplied as an empty sequence.
See 7.5 fn:resolve-uri
The 3rd, 4th, and 5th arguments are now optional; previously the function required either 2 or 5 arguments.
See 9.8.1 fn:format-dateTime
See 9.8.2 fn:format-date
See 9.8.3 fn:format-time
All three arguments are now optional, and each argument can be set to an empty sequence. Previously if $description was supplied, it could not be empty.
See 21.1.1 fn:error
The $label argument can now be set to an empty sequence. Previously if $label was supplied, it could not be empty.
See 21.2.1 fn:trace
PR 905
The rule that multiple calls on fn:doc supplying the same absolute URI must return the same document node has been clarified; in particular the rule does not apply if the dynamic context for the two calls requires different processing of the documents (such as schema validation or whitespace stripping).
See 17.1.1 fn:doc
PR 909
The function has been expanded in scope to handle comparison of values other than strings.
See 2.2.2 fn:compare
PR 924
Rules have been added clarifying that users should not be allowed to change the schema for the fn namespace.
See D Schemas
PR 925
The decimal format name can now be supplied as a value of type xs:QName, as an alternative to supplying a lexical QName as an instance of xs:string.
See 4.7.2 fn:format-number
PR 932
The specification now prescribes a minimum precision and range for durations.
See 8.1.2 Limits and precision
PR 933
When comments and processing instructions are ignored, any text nodes either side of the comment or processing instruction are now merged prior to comparison.
See 2.2.4 fn:deep-equal
PR 940
New in 4.0
See 2.5.20 fn:subsequence-where
PR 953
Constructor functions for named record types have been introduced.
See 22.6 Constructor functions for named record types
PR 962
New in 4.0
See 2.5.2 fn:do-until
See 2.5.23 fn:while-do
PR 969
New in 4.0
See 14.4.3 map:empty
PR 984
New in 4.0
See 8.4.1 fn:seconds
PR 987
The order of results is now prescribed; it was previously implementation-dependent.
See 2.2.5 fn:distinct-values
PR 1022
Regular expressions can include comments (starting and ending with #) if the c flag is set.
See 6.1 Regular expression syntax
See 6.2 Flags
PR 1028
An option is provided to control how the JSON null value should be handled.
See 17.4.4 fn:parse-json
PR 1032
New in 4.0
See 2.1.17 fn:void
PR 1046
New in 4.0
See 2.5.21 fn:take-while
PR 1059
Use of an option keyword that is not defined in the specification and is not known to the implementation now results in a dynamic error; previously it was ignored.
See 1.7 Options
PR 1068
New in 4.0
See 5.4.3 fn:graphemes
PR 1072
The return type is now specified more precisely.
See 18.2 fn:load-xquery-module
PR 1090
When casting from a string to a duration or time or dateTime, it is now specified that when there are more digits in the fractional seconds than the implementation is able to retain, excess digits are truncated. Rounding upwards (which could affect the number of minutes or hours in the value) is not permitted.
See 23.2 Casting from xs:string and xs:untypedAtomic
PR 1093
New in 4.0
See 5.3.9 fn:collation
PR 1117
The $options parameter has been added.
See 17.1.5 fn:unparsed-text
See 17.1.7 fn:unparsed-text-available
PR 1182
The $predicate callback function may return an empty sequence (meaning false).
See 2.5.2 fn:do-until
See 2.5.3 fn:every
See 2.5.4 fn:filter
See 2.5.10 fn:index-where
See 2.5.16 fn:some
See 2.5.21 fn:take-while
See 2.5.23 fn:while-do
See 14.4.6 map:filter
See 14.4.12 map:keys-where
See 15.2.4 array:filter
See 15.2.14 array:index-where
PR 1191
The $options parameter has been added, absorbing the $collation parameter.
See 2.2.4 fn:deep-equal
New in 4.0
See 12.3.1 fn:distinct-ordered-nodes
PR 1250
For selected properties including percent and exponent-separator, it is now possible to specify a single-character marker to be used in the picture string, together with a multi-character rendition to be used in the formatted output.
See 4.7.2 fn:format-number
PR 1257
The $options parameter has been added.
See 17.2.1 fn:parse-xml
See 17.2.2 fn:parse-xml-fragment
PR 1262
New in 4.0
See 5.3.10 fn:collation-available
PR 1265
The constraints on the result of the function have been relaxed.
See 12.1.2 fn:document-uri
PR 1280
As a result of changes to the coercion rules, the number of supplied arguments can be greater than the number required: extra arguments are ignored.
See 2.5.1 fn:apply
PR 1288
Additional error conditions have been defined.
See 17.2.1 fn:parse-xml
PR 1296
New in 4.0
See 2.5.14 fn:scan-left
PR 1333
A new option is provided to allow the content of the loaded module to be supplied as a string.
See 18.2 fn:load-xquery-module
PR 1353
An option has been added to suppress the escaping of the solidus (forwards slash) character.
See 17.4.7 fn:xml-to-json
PR 1358
New in 4.0
See 9.3.2 fn:unix-dateTime
PR 1361
The term atomic value has been replaced by atomic item.
See 1.9 Terminology
PR 1393
Changes the function to return a sequence of key-value pairs rather than a map.
See 13.5 fn:function-annotations
PR 1409
This section now uses the term primitive type strictly to refer to the 20 atomic types that are not derived by restriction from another atomic type: that is, the 19 primitive atomic types defined in XSD, plus xs:untypedAtomic. The three types xs:integer, xs:dayTimeDuration, and xs:yearMonthDuration, which have custom casting rules but are not strictly-speaking primitive, are now handled in other subsections.
See 23.1 Casting from primitive types to primitive types
The rules for conversion of dates and times to strings are now defined entirely in terms of XSD 1.1 canonical mappings, since these deliver exactly the same result as the XPath 3.1 rules.
See 23.1.2.2 Casting date/time values to xs:string
The rules for conversion of durations to strings are now defined entirely in terms of XSD 1.1 canonical mappings, since the XSD 1.1 rules deliver exactly the same result as the XPath 3.1 rules.
See 23.1.2.3 Casting xs:duration values to xs:string
PR 1455
Numbers now retain their original lexical form, except for any changes needed to satisfy JSON syntax rules (for example, stripping leading zero digits).
See 17.4.7 fn:xml-to-json
PR 1473
New in 4.0
See 2.1.5 fn:identity
PR 1481
The function has been extended to handle other Gregorian types such as xs:gYearMonth.
See 9.5.1 fn:year-from-dateTime
See 9.5.2 fn:month-from-dateTime
The function has been extended to handle other Gregorian types such as xs:gMonthDay.
See 9.5.3 fn:day-from-dateTime
The function has been extended to handle other types including xs:time.
See 9.5.4 fn:hours-from-dateTime
See 9.5.5 fn:minutes-from-dateTime
The function has been extended to handle other types such as xs:gYearMonth.
See 9.5.7 fn:timezone-from-dateTime
PR 1504
Optional $separator added.
See 15.2.17 array:join
PR 1523
New functions are provided to obtain information about built-in types and types defined in an imported schema.
See 19 Processing types
New in 4.0
See 19.1.2 fn:schema-type
See 19.1.4 fn:atomic-type-annotation
See 19.1.5 fn:node-type-annotation
PR 1545
New in 4.0
See 9.6.4 fn:civil-timezone
PR 1565
The default for the escape option has been changed to false. The 3.1 specification gave the default value as true, but this appears to have been an error, since it was inconsistent with examples given in the specification and with tests in the test suite.
See 17.4.4 fn:parse-json
PR 1570
New in 4.0
See 19.1.3 fn:type-of
PR 1587
New in 4.0
See 17.1.8 fn:unparsed-binary
PR 1611
The spec has been corrected to note that the function depends on the implicit timezone.
See 2.2.2 fn:compare
PR 1671
New in 4.0.
See 4.4.3 fn:divide-decimals
PR 1687
New in 4.0
See 14.4.10 map:items
PR 1703
Ordered maps are introduced.
See 14.1 Ordering of Maps
Enhanced to allow for ordered maps.
See 14.4.6 map:filter
See 14.4.7 map:find
See 14.4.8 map:for-each
See 14.4.14 map:put
See 14.4.15 map:remove
The order of entries in maps is retained.
See 17.4.4 fn:parse-json
PR 1711
It is explicitly stated that the limits for $precision are implementation-defined.
See 4.4.6 fn:round
See 4.4.7 fn:round-half-to-even
PR 1727
For consistency with the new function map:build, the handling of duplicates may now be controlled by supplying a user-defined callback function as an alternative to the fixed values for the earlier duplicates option.
See 14.4.13 map:merge
PR 1734
In 3.1, given a mixed input sequence such as (1, 3, 4.2e0), the specification was unclear whether it was permitted to add the first two integer items using integer arithmetic, rather than converting all items to doubles before performing any arithmetic. The 4.0 specification is clear that this is permitted; but since the items can be reordered before being added, this is not required.
See 2.4.4 fn:avg
See 2.4.7 fn:sum
PR 1825
New in 4.0
See 2.5.12 fn:partial-apply
PR 1856
Word boundaries can be matched. Lookahead and lookbehind assertions are supported. Assertions (including ^ and $) can no longer be followed by a quantifier.
See 6.1 Regular expression syntax
The output of the function is extended to allow the represention of captured groups found within lookahead assertions.
See 6.3.4 fn:analyze-string
PR 1879
Additional options to control DTD and XInclude processing have been added.
See 17.2.1 fn:parse-xml
PR 1897
The $replacement argument can now be a function that computes the replacement strings.
See 6.3.2 fn:replace
PR 1906
New in 4.0
See 14.5.10 fn:element-to-map-plan
New in 4.0.
See 14.5.11 fn:element-to-map
PR 1910
An $options parameter is added. Note that the rules for the $options parameter control aspects of processing that were implementation-defined in earlier versions of this specification. An implementation may provide configuration options designed to retain backwards-compatible behavior when no explicit options are supplied.
See 17.1.1 fn:doc
See 17.1.2 fn:doc-available
PR 1913
It is now permitted for the regular expression to match a zero-length string.
See 6.3.2 fn:replace
See 6.3.3 fn:tokenize
See 6.3.4 fn:analyze-string
PR 1933
New in 4.0
See 17.2.5 fn:xsd-validator
PR 1991
Named record types used in the signatures of built-in functions are now available as standard in the static context.
See C Built-in named record types
PR 2001
New in 4.0.
See 2.5.18 fn:sort-by
See 15.2.26 array:sort-by
PR 2013
Support for binary input has been added.
See 17.2.1 fn:parse-xml
See 17.2.2 fn:parse-xml-fragment
New in 4.0
See 17.3.3 fn:html-doc
See 17.5.8 fn:csv-doc
PR 2030
This description of the XSD validation process was previously found (with some duplication) in the XQuery and XSLT specifications; those specifications now reference this description. As a side-effects, the descriptions of the process in XQuery and XSLT are better aligned.
See 17.2.4 XSD validation
PR 2031
Introduced the concept of JNodes.
See 16 Processing JNodes
New in 4.0
See 16.1.1 fn:jtree
See 16.1.3 fn:jnode-selector
See 16.1.4 fn:jnode-position
PR 2149
Generalized to work with JNodes as well as XNodes.
See 12.2.1 fn:has-children
The function is extended to handle JNodes.
See 12.2.9 fn:path
Generalized to work with JNodes as well as XNodes.
See 12.3.2 fn:innermost
See 12.3.3 fn:outermost
PR 2168
Atomic items of types xs:hexBinary and xs:base64Binary are now mutually comparable. In rare cases, where an application uses both types and assumes they are distinct, this can represent a backwards incompatibility.
See 2.2.1 fn:atomic-equal
See 2.2.4 fn:deep-equal
See 2.2.5 fn:distinct-values
PR 2223
An error may now be raised if the base URI is not a valid LEIRI reference.
See 12.1.1 fn:base-uri
PR 2224
The $action callback function now accepts an optional position argument.
See 14.4.6 map:filter
See 14.4.8 map:for-each
PR 2228
New in 4.0
See 15.2.27 array:sort-with
PR 2249
The specification now describes in more detail how to determine the effective encoding value.
See 17.1.5 fn:unparsed-text
PR 2256
In the interests of consistency, the index-of function now defines equality to mean contextually equal. This has the implication that NaN is now considered equal to NaN.
See 2.2.8 fn:index-of
PR 2259
A new parameter canonical is available to give control over serialization of XML, XHTML, and JSON.
See 17.2.3 fn:serialize
PR 2286
The type of $value has been generalized to xs:anyAtomicType?.
See 5.4.7 fn:string-length
See 5.4.8 fn:normalize-space
PR 2387
It is now recommended that out-of-range xs:double values should translate to positive or negative infinity.
See 17.4.4 fn:parse-json
PR 2387
It is now recommended that out-of-range xs:double values should translate to positive or negative infinity.
See 17.4.4 fn:parse-json

XPath and XQuery Functions and Operators 4.0

W3C Editor's Draft 23 February 2026

Abstract

Status of this Document

Dedication

17 External resources and data formats

17.4 Functions on JSON Data

17.4.4 fn:parse-json

H Changes since 3.1 (Non-Normative)

H.1 Summary of Changes