Recursive entity representation in JSON schema.

[mitchell....@gmail.com]

Hi Everyone,

I have recently been doing some reading about JSON schema because I
am very interested in utilizing it rather than XML (mostly due to my
desire to work with very specific open source software). My
question is focused around statements that a JSON schema can NOT
facilitate a recursive structure. This is a problem for my data
representation because I need to convert the following scenario from
XML to JSON.. (this is a sample XML, not my actual data-set)

<tns:Folder name="Library">
<tns:Folder name="Documents">
<tns:Folder name="CIS2250">
<tns:File name="TechManual.pdf" />
<tns:File name="UserManual.pdf" />
</tns:Folder>
<tns:File name="MyFile1.txt" />
<tns:File name="MyFile2.txt" />
<tns:File name="MyFile3.txt" />
</tns:Folder>
<tns:Folder name="Downloads">
<tns:File name="EatMyShorts.mpeg" />
<tns:File name="BackToTheFuture-Part1.avi" />
<tns:File name="" />
</tns:Folder>
</tns:Folder>

Notice that the tns:Folder XML entity can be recursively represented
in a XML schema. After the XML Schema definition I utilize a tool
called Jibx to automatically create clone Java classes, and then
populate those classes with instances of a XML instance during
execution of my program.

Overall my question is... can an entity within a JSON schema hold a
collection of a it's own entity classification? Some online
publications have suggested to utilize YAML instead of JSON, but for
my purposes the decision lies between XML or JSON.

All the best,
Mitch

[Kenny Hoxworth]

JSON Schema can most definitely handle recursive structures as of draft-03. Draft-03 introduced the "$ref" attribute, which allows a schema to reference another schema (or itself) to validate against. In the case of a filesystem hierarchy, assume a JSON representation of the data as follows:

{

  "type" : "folder",

  "name" : "documents",

  "contents" : [

    {

      "type" : "folder",

      "name" : "testDir",

      "contents" : []

    },

    {

      "type" : "file",

      "name" : "test.txt"

    }

  ]

}

As JSON schema that represents this data would be as follows:

{

  "type" : "object",

  "id" : "folder",

  "additionalProperties" : false,

  "properties" : {

    "name" : { "required" : true, "type" : "string" },

    "type" : { "required" : true, "type" : "string", "enum" : ["folder"] },

    "contents" : {

      "required" : true,

      "type" : "array",

      "additionalItems" : false,

      "items" : [

        { "$ref" : "folder" },

        {

          "type" : "object",

          "id" : "file",

          "additionalProperties" : false,

          "properties" : {

            "name" :  { "required" : true, "type" : "string" },

            "type" : { "required" : true, "type" : "string", "enum" : ["file"] }

          }

        }

      ]

    }

  }

}

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[yott...@gmail.com]

Does anyone know a tool that will generate Java from a recursive JSON instance without duplicating classes, or will generate tight JSON schema from recursive JSON instances?

Thanks,

John Carlson