JSONiq

JSONiq primarily provides means to extract and transform data from JSON documents or any data source that can be viewed as JSON (e.g. relational databases or web services).

The major expression for performing such operations is the SQL-like “FLWOR expression” that comes from XQuery. A FLWOR expression is constructed from the five clauses after which it is named: FOR, LET, WHERE, ORDER BY, RETURN. However, it also supports clauses for doing grouping and windowing.

The language also provides syntax for constructing new JSON documents where either the field names and values are known in advance or can be computed dynamically. The JSONiq language (not the extension to XQuery) is a superset of JSON. That is, each JSON document is a valid JSONiq program.

Additionally, the language also supports a navigational syntax for extracting field names and values out of JSON objects as well as values out of JSON arrays. Navigation is resilient in the absence of values, or if values are heterogeneous, in that it silently ignores unforeseen values without raising errors.

All constructs are defined as expressions within the language and can be arbitrarily nested.

JSONiq does not include features for updating JSON or XML documents, it does not have full text search capabilities, and has no statements. All of these features are under active development for a subsequent version of the language.

JSONiq is a programming language that can express arbitrary JSON to JSON or XML to XML transformations. It also allows for transformations between JSON and XML. All such transformations have the following features:

1. Logical/physical data independence
2. Declarative
3. High level
4. Side-effect free
5. Strongly typed

The sample JSONiq code below computes the area code and the number of all people older than 20 from a collection of JSON person objects (see the JSON article for an example object).

 for $p in collection("persons")
 where $p.age gt 20
 let $home := $p.phoneNumber[][$$.type eq "home"].number
 group by $area := substring-before($home, " ")
 return 
   {
     "area code" : $area,
     "count" : count($p)
   }

All JSONiq constructs are expressions and can also be contained in the body of a function.

 declare function local:adults()
 {
   for $p in collection("persons")
   where $p.age gt 20
   return $p
 };

The next query transforms parts of each person object into an XML element using the XQuery syntax (JSONiq extension to XQuery).

 for $p in collection("persons")
 return 
   <person>
     <firstName>{$p("firstName")}</firstName>
     <lastName>{$p("lastName")}</lastName>
     <age>{$p("age")}</age>
   </person>

Below are a few examples of how and where JSONiq can be used:

1. Extracting information out of a database to use in a web service.
2. Generating summary reports on data stored in a JSON document store.
3. Selecting and transforming JSON data to XHTML to be published on the Web.
4. Correlating data from various sources and formats (e.g. JSON document store, XML database, relational database, and web service) and offer it in a web service.
5. Transforming collections of JSON objects into a different schema.

There are two syntaxes of JSONiq, which users can use on whether they are focusing on JSON or XML. Both syntaxes use the same data model and are very similar up to a few exceptions.

• JSONiq - The SQL of NoSQL. Ghislain Fourny. CreateSpace Independent Publishing Platform. ISBN 1489530371.

• Zorba: JSONiq and JSONiq Extension to XQuery
• IBM WebSphere: JSONiq extension to XQuery
• BeniBela Internet Tools: JSONiq extension to XQuery