Table of Contents
JSONiq is a query language that was specifically designed for querying JSON, although its data model is powerful enough to handle more similar formats.
As stated on json.org, JSON is a "lightweight data-interchange format. It is easy for humans to read and write. It is easy for machines to parse and generate."
A JSON document is made of the following building blocks: objects, arrays, strings, numbers, booleans and nulls.
JSONiq manipulates sequences of these building blocks, which are called items. Hence, a JSONiq value is a sequence of items.
Any JSONiq expression takes and returns sequences of items.
Comma-separated JSON-like building blocks is all you need to begin building your own sequences. You can mix and match, as JSONiq supports heterogeneous sequences seamlessly.
Example 1. A sequence
"foo", 2, true, { "foo", "bar" }, null, [ 1, 2, 3 ]
Result: foo 2 true foo bar null [ 1, 2, 3 ]
Sequences are flat and cannot be nested. This makes streaming possible, which is very powerful.
Example 2. Sequences are flat
( ("foo", 2), ( (true, 4, null), 6 ) )
Result: foo 2 true 4 null 6
A sequence can be empty. The empty sequence can be constructed with empty parentheses.
Example 3. The empty sequence
()
Result:
A sequence of just one item is considered the same as just this item. Whenever we say that an expression returns or takes one item, we really mean that it takes a singleton sequence of one item.
Example 4. A sequence of one item
("foo")
Result: foo
JSONiq classifies the items mentioned above in three categories:
Atomic items: strings, numbers, booleans and nulls, but also many other supported atomic values such as dates, binary, etc.
Structured items: objects and arrays.
Function items: items that can take parameters and, upon evaluation, return sequences of items.
The JSONiq data model follows the W3C specification, but, in core JSONiq, does not include XML nodes, and includes instead JSON objects and arrays. Engines are free, however, to optionally support XML nodes in addition to JSON objects and arrays.