Introduction
In this specification, we detail the JSONiq language in version 1.0. Historically, JSONiq was first created as an extension to XQuery. Later, a separate core syntax was created which makes it 100% tailored for JSON. It is the JSONiq core syntax that is detailed in this document.
The functionality directly inherited from XQuery is described on a higher level and we explicitly refer for more in-depth details to the W3C specification.
Structure of a JSONiq program.
A JSONiq program can either be a main module, which contains a query that can be executed, or a library module, which defines functions and variables that can be used in other modules.
A main or library module can be optionally prefixed with a JSONiq declaration with a version (currently 1.0) and an encoding.
Module
Main modules
A JSONiq main module is made of two parts: an optional prolog, and an expression, which is the main query.
MainModule
The result of the main JSONiq program is the result of its main query.
In the prolog, it is possible to declare global variables and functions. Mostly, you will recognize a prolog declaration by the semi-colon it ends with. The main query does not contain semi-colons (at least in core JSONiq).
Global variables and functions can use and call each other arbitrarily, even if the dependency is further down in the prolog. If there a cycle, an error is thrown.
JSONiq largely follows the W3C standard regarding modules. The detailed specification is found here.
Library modules
Library modules do not contain any main query, just global variables and functions. They can be imported by other modules.
A library module is introduced with a module declaration, followed by the prolog containing its variables and functions.
LibraryModule
Feature matrix
JSONiq is 99% reliant on XQuery, a W3C standard. For everything taken over from the W3C standard, a brief, non-normative explanation is provided with a link to the corresponding part in the W3C specification.
JSONiq Data Model
Atomic items
W3C-conformant
Structured items
JSONiq-specific
Function items
W3C-conformant
Node items (XML)
Omitted (optional support by some engines)
JSONiq Type System
Atomic types
W3C-conformant, but support for xs:ID, xs:IDREF, xs:IDREFS, xs:Name, xs:NCName, xs:ENTITY, xs:ENTITIES, xs:NOTATION omitted (except for engines also supporting XML)
js:null type
JSONiq-specific
js:item, js:atomic types
JSONiq-specific synonyms for item() and xs:anyAtomicType
Structured types
JSONiq-specific
Function types
W3C-conformant
Empty sequence type
JSONiq-specific notation () for empty-sequence()
XML node types
Omitted (optional support by engines supporting XML)
Concepts
Effective boolean value
W3C-conformant, extended with object, array and null semantics
Atomization
Omitted (optional support by engines supporting XML)
Expressions
Numeric literals
W3C-conformant
String literals
W3C-conformant, but escape is done with \ not with &
Boolean and null literals
JSONiq-specific
Variable reference
W3C-conformant
Parenthesized expressions
W3C-conformant
Context item expressions
W3C-conformant but $$ syntax instead of .
Static function calls
W3C-conformant
Named function reference
W3C-conformant
Inline function expressions
W3C-conformant
Filter expressions
W3C-conformant
Dynamic function calls
W3C-conformant
Path expressions (XML)
Omitted (optional support by engines supporting XML, but relative paths must start with ./)
Object lookup
JSONiq-specific
Array lookup
JSONiq-specific
Array unboxing
JSONiq-specific
Sequence expressions
W3C-conformant
Arithmetic expressions
W3C-conformant, no atomization needed (except for engines also supporting XML)
String concatenation expressions
W3C-conformant
Comparison expressions
W3C-conformant, no need to atomize or convert from untyped and untypedAtomic (except for engines also supporting XML)
Logical expressions
W3C-conformant
XML constructors
Omitted (optional support by engines supporting XML)
JSON (object and array) constructors
JSONiq-specific
FLWOR expressions
W3C-conformant
Unordered and ordered expressions
W3C-conformant
Conditional expressions
W3C-conformant
Switch expressions
W3C-conformant
Quantified expressions
W3C-conformant
Try-catch expressions
W3C-conformant
Instance-of expressions
W3C-conformant
Typeswitch expressions
W3C-conformant
Cast expressions
W3C-conformant
Castable expressions
W3C-conformant
Constructor functions
W3C-conformant, additional constructor function for null()
Treat expressions
W3C-conformant
Simple map operator
W3C-conformant
Validate expressions
Omitted (optional support by engines supporting XML)
Extension expressions
W3C-conformant
Static context
XPath 1.0 compatibility mode
Omitted (optional support by engines supporting XML)
Statically known namespaces
W3C-conformant
Default element/type namespace
W3C-conformant, strong recommendation for implementations to overwrite with the proxy namespace http://jsoniq.org/default-type-namespace to omit prefixes.
Default function namespace
W3C-conformant, strong recommendation for implementations to overwrite with http://jsoniq.org/default-function-namespace to omit prefixes.
In-scope schema definitions
Omitted (optional support by engines supporting XML)
In-scope variables
W3C-conformant
Context item static type
W3C-conformant
Statically known function signatures
W3C-conformant, augmented with all JSONiq builtin functions
Statically known collations
W3C-conformant
Default collation
W3C-conformant
Construction mode
Omitted (optional support by engines supporting XML)
Ordering mode
W3C-conformant
Default order for empty sequences
W3C-conformant
Boundary-space policy
Omitted (optional support by engines supporting XML)
Copy-namespaces mode
Omitted (optional support by engines supporting XML)
Static Base URI
W3C-conformant
Statically known documents
Omitted (optional support by engines supporting XML)
Statically known collections
Omitted (optional support by engines supporting XML)
Statically known default collection type
Omitted (optional support by engines supporting XML)
Statically known decimal formats
W3C-conformant
Dynamic context
Context item
W3C-conformant (but with syntax $$ not .)
Initial context item
W3C-conformant
Context position
W3C-conformant
Context size
W3C-conformant
Variable values
W3C-conformant
Named functions
W3C-conformant
Current dateTime
W3C-conformant
Implicit timezone
W3C-conformant
Default language
W3C-conformant
Default calendar
W3C-conformant
Default place
W3C-conformant
Available documents
Omitted (optional support by engines supporting XML)
Available text resources
W3C-conformant
Available node collections
Omitted (optional support by engines supporting XML)
Default node collection
Omitted (optional support by engines supporting XML)
Available resource collections
Omitted (optional support by engines supporting XML)
Default resource collection
Omitted (optional support by engines supporting XML)
Environment variables
W3C-conformant
Namespaces
The namespace http://jsoniq.org/functions is used for JSONiq builtin functions defined by this specification. This namespace is exposed to the user and is bound by default to the prefix jn. For instance, the function name jn:keys() is in this namespace.
The namespace http://jsoniq.org/types is used for JSONiq builtin types defined by this specification (including synonyms for some XQuery types). This namespace is exposed to the user and is bound by default to the prefix js. For instance, the type name js:null is in this namespace.
The namespace http://jsoniq.org/default-function-namespace is a proxy namespace that maps to the jn: (JSONiq), fn: (XQuery) and math: (XQuery) namespaces. It is the default function namespace, allowing to call all these functions with no prefix.
The namespace http://jsoniq.org/default-type-namespace is a proxy namespace that maps to the js: (JSONiq) and xs: (XQuery) namespaces. It is the default type namespace, allowing to use all builtin types with no prefix.
Accessors used in JSONiq Data Model use the jdm: prefix. These functions are not exposed to the user and are for explanatory purposes of the data model within this document only. The jdm: prefix is not associated with a namespace.
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