Re: [Json] Another problematic JSON Schema use-case

This is a problem that I tried working on a year or two ago, but couldn't
find any good resolution to.

Let's create a JSON Schema for the described problem (slightly
modified/expanded for illustration below):

{
"type": "object",
"additionalProperties": {
"type": "object",
"properties": {"Type":{"enum":["Animal", "Vegetable", "Mineral"]}},
"required": ["Type"],
"oneOf": [
{
"properties": {
"Type":{"enum":["Animal"]},
"Thermoregulation":{"enum":["Endotherm", "Ectotherm"]}
},
"required": ["Thermoregulation"]
},
{
"properties": {
"Type":{"enum":["Vegetable"]},
"Organic":{"type":"number"}
},
"required": ["Organic"]
},
{
"properties": {
"Type":{"enum":["Mineral"]},
"Organic":{"type":"boolean"}
},
"required": ["Organic"]
}
]
}
}

Here's a valid instance for illustration:

{
"o1": {
"Type": "Animal",
"Thermoregulation": "Endotherm",
"Species": "Felis catus",
"Label": "cat"
},
"o2": {
"Type": "Mineral",
"Organic": false,
"Label": "Quartz"
}
}

This, however, is an invalid instance:

{
"o3": {
"Type": "Vegetable",
"Endotherm": true,
"Label": "Silver"
}
}

What sort of error would be appropriate here? (E.g. Is this a typo for the
"Type" property? Or is this just missing a required "Organic" property?)

When I run it through my validator, I get this error:

(1 of 1) instance.o3 is not exactly one from <http://example.org/Animal>,<
http://example.org/Vegetable>,<http://example.org/Mineral>

And within all three schemas, exactly one constraint fails. So which one do
we suggest errors for? Changing 'Vegetable' to 'Animal', and changing
'Endotherm' to 'Organic' are all equally reasonable (to a computer)
one-word fixes.

In general, JSON Schema and many other schemas are designed to ensure
things are valid. They're not well engineered to help people fix things
when they're invalid.

A similar problem is that localizing error strings. There's a few
suggestions to add custom error strings to JSON Schema, but then we have
the problem that they're not localized. If we allow multiple strings (one
per localization), then we have to update the schema every time we add a
locale, which means changing the file even though nothing about the schema
has changed.

I just created <
https://github.com/json-schema-org/json-schema-spec/issues/31> to look at
this problem as it relates to JSON Schema.

Cheers,

Austin Wright.

On Sun, May 22, 2016 at 11:15 AM, Tim Bray <tbray@textuality.com> wrote:

> See https://www.tbray.org/ongoing/When/201x/2016/05/22/Json-Schema-Gripe
>
>
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