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Comment by tored | Hacker News Reader

One thing I'm guilty of is designing a document format as JSON, thus the need to formally verify it.

Passing data works well as JSON but documents works better as XML where you can use XML Schema.

This is where I would also develop an XML variant, even if it is never to be used, simply so that I can have a Schema to go along with it. I'll start with a data structure/class, in the code, then use a built-in transformer, to turn it into JSON or XML. That way, I know that the "kernel" of the data is the same, between them.

Even though JSON is a "natural" for scalar types, it can get weird, there. For example, let's say we have a float:

    { "kids": 1.0 }

It needs to be parsed as a float, because we could have:

    { "kids": 2.3 }

But I often see these sent as:

    { "kids": 1 }

    { "kids": "1.0" }

or even

    { "kids": "1" }

And I have differing results, based on the parser.

Even with integers (comes up often for large numeric IDs):

   JSON.stringify(JSON.parse('{"kids":10000000000000001}')) -> '{"kids":10000000000000000}'

How do JSON schemas handle "must be an integer", and having to pass a string to get the necessary value?

I think you can use a string type with a regexp pattern.

That’s not an issue with json, but with json libraries. For better or (IMO) for worse

  {“kids”: 12345678901234567890123456789012345678901234567890}

is perfectly legal json.

If every JSON library actively chooses not to implement the JSON spec, that sounds like an issue with JSON to me.

More precisely, an issue with different literal types instead of one like in XML.

In XML, every attribute or text fragment is a string, to be POSSIBLY parsed as a string, integer, date etc. according to what applications choose to do (usually according to an explicit schema).

In JSON, YAML, etc. there are at least integers, strings and floating point numbers, introducing arbitrary representation choices (1, 1.0, "1", "1.0") and implementation artifacts (e.g. numerical limits).

Separate types is fine, but JSON doesn't specify a minimum range or precision of the number type that a implementation must have, so the number type is unreliable (and string has to be used instead). To handle any number, a JSON library needs to use an arbitrary-precision number type, which no common one does because of the huge performance hit.

So, no better than XML really :D

Look at MongoDBs "extended json". They serialize this as { "$numberLong": "10000000000000001" }.

With a custom extension to the json-schema adding property bsonType:long, instead of type:int. Along with a few other data types like datetimes, uuid, regex. It can be integrated with custom hooks in many schema validators.

Perhaps create your own custom type floatable that can be either be of type float, integer or string with a regexp pattern.

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