number representation in JSONLD

[VladimirAlexiev]

(split off from #49)

in JSONLD it must be 1.23 and not "1.23" for a float.

I wrote in 3lbits/CIM4NoUtility#278 about the dangers of JSON numbers.
JSON doesn't define its numbers:

• It doesn't define int, float, double: there's just "number".
• And it doesn't specify whether a number should be represented as float, double or even infinite precision big decimal.
  That is implementation specific.

https://json-ld.org/playground/

1. Convert this to NQuads :

{
  "@context": {
    "cim": "http://iec.ch/TC57/CIM100#"
  },
  "@graph": [{
    "@id": "urn:uuid:9d58e5bb-834c-4faa-928c-7da0bb1497d9",
    "cim:Equipment.normallyInService": true,
    "cim:Reactance.value": [0.123, 1.00000000000]
    }]}

The result is "0.123"^^xsd:double and "1"^^xsd:integer.
So depending on the specific value, it's treated as different datatype!

2. Only if we add specific datatypes (in the context):

{
  "@context": {
    "cim": "http://iec.ch/TC57/CIM100#",
    "xsd": "http://www.w3.org/2001/XMLSchema#",
    "cim:Equipment.normallyInService": {"@type": "xsd:boolean"},
    "cim:Reactance.value": {"@type": "xsd:float"}
  },
  "@graph": [{
    "@id": "urn:uuid:9d58e5bb-834c-4faa-928c-7da0bb1497d9",
    "cim:Equipment.normallyInService": true,
    "cim:Reactance.value": [0.12345678901234567890, 1.00000000000]
    }]}

We get what we want: "1.234567890123457E-1"^^xsd:float and "1"^^xsd:float.
But 1.234567890123457E-1 has too many decimals for a float. What happened is that internally it was processed as double, and only spit out with float datatype.

3. More importantly, you cannot control whether to enclose numbers in quotes on output.
   I made tests with some tools (I'll commit the details to git):

tool	reactance	normallyInService
GraphDB	"0.123" xsd:float	"true" xsd:boolean
Jena riot	"0.123" xsd:float	"true" xsd:boolean
ttl2json	"0.123" xsd:float	true
Virtuoso context	0.1230000033974648	true
Virtuoso plain	0.1230000033974648	true

• GraphDB and Jena output @value in quotes and always attach a datatype
• Virtuoso outputs only @value without quotes (and adds some fake decimal digits due to internal conversions)
• ttl2json outputs the number as @value in quotes with datatype, but the boolean without quotes

Note: in all cases we didn't specify a context to use (because it's not ready).
If we do, then more tools may output values in quotes.

---

What is the harm if JSON numbers are enclosed in quotes?

[Sveino]

Does this example not show that we "must" allow for both?

My understanding is:
The JSON-LD standard specifies that datatype declarations can be used to define the type of literal values, such as integers, dates, or custom data types, by adding a "@type" key within the context or within each value. This is optional in JSON-LD, as JSON-LD tries to be flexible with datatypes to accommodate varied data structures and maximize compatibility with JSON.

From this we have the following option:

1. Requiring Datatype Declarations
2. Not Allowing Datatype Declarations
3. Allowing Both With and Without Datatypes

As we have the context as part of the profile I do not see that we have to require it (1). However, interoperability is fundamental so that is pointing to requiring it. For me I would recommend (3) - Allowing both.

Virtuoso behaviours is generally not accepted. However, I think we have in CIM standard defined some tolerance that this would be inside.