Hi Marco,

I am not quite sure if I understand your question well, but let me make a couple of remarks about the rationale of treating JSON as XML.

XML is accessible to XPath, nested maps and arrays are not. Hence any non-trivial navigation of XML trees is incomparably simpler and more elegant than navigation of JSON trees, representated by nested maps and arrays. Similarly, the *construction* of complex XML structure is often much simpler than the construction of nested maps and arrays. As a consequence, the processing of JSON can often be radically simplified by dealing with XML, rather than JSON: just frame your processing between an initial JSON to XML transformation (json:parse) and a final XML to JSON transformation (json:serialize).

It is important to realize that there are alternative XML representations of JSON. The representation defined in the XSLT 3.0 spec is very "clean" from a conceptual point of view, but navigation-unfriendly, as the all important object member names are represented by attributes, rather than element names (which are restricted to "map", "array", "string", "number", "boolean", umph!), resulting in a rather cluttered representation, requiring clumsy XPath expressions. The alternative representation offered by BaseX [1], on the other hand, looks intuitive and enables navigation which is in typically cases as elegant as if the data were supplied in XML to begin with. I can highly recommend dealing with JSON via the BaseX XML representation, and I use this XML format also in the construction of JSON.

An advantage of the map/array representation is higher performance, which may become important especially when dealing with very large documents.

Wrapping up, it is very important to have access to both principal kinds of JSON representation in XQuery, maps/array and XML.

Kind regards,

Hans-Jürgen

[1] http://docs.basex.org/wiki/JSON_Module#BaseX_Format

PS: If you are interested in a discussion comparing navigation of JSON represented by maps/arrays versus XML, you might consider reading here:

http://www.balisage.net/Proceedings/vol15/html/Rennau01/BalisageVol15-Rennau01.html#xml-binding

Marco Lettere <marco.lettere@dedalus.eu> schrieb am 21:54 Donnerstag, 15.Oktober 2015:

Hi all,

I have a bit of difficulty in understanding the rationale behind the XML to Json (and vice-versa) conversions.

I must admit I'm a bit confused on when to use which format and how those map to serialization/parsing rules.

In particular I'm wondering whether it's really necessary to use both the formalisms (and functions) in the following example.

My feelings are that using only the standard (?) XQuery 3.1 representation would be much clearer and would enable a cleaner service chaining mechanism.

Has anyone 2 minutes left to explain to me the model behind this sort of things?

I really appreciate your support!

Regards,

Marco.

module namespace jt = "urn:json:test";

declare

  %rest:path("jsonsrv")

  %output:method("text")

  %output:media-type("application/json")

function jt:service()

{

  xml-to-json(

    <map xmlns="http://www.w3.org/2005/xpath-functions">

      <string key="a">12345678</string>

    </map>)

};

declare

  %rest:path("testreq")

  %output:method("text")

  %output:media-type("application/json")

function jt:test()

{

  let $response := http:send-request(

    <http:request href="http://localhost:9984/jsonsrv" method="POST">

      <http:body media-type="application/x-www-form-urlencoded" method="text"/>

    </http:request>)

  return json:serialize($response[2])

};