default annotation

[codalogic]

(Even lower priority?)

Similar to the situation with the minExclusive and maxExclusive issue (#119), JSON Schema (+ XSD, but not in the base of Relax NG) has a default property.

If this were thought useful for JCR, it could be another annotation. For example:

"required" : @{default false} boolean ?,
"country" : @{default "USA"} string ?,
"state" : @{default $closed} ( "open" | $closed ) ?
$closed = "closed"

I hope limiting the feature to primitive types would be sufficient, especially as braces can't go in annotations. If object default were thought to be necessary, we could do something like:

"address" : @{default $downing-street} $address ?,
$downing-street = { "number" : 10, "street" : "Downing Street", "town" : "London" }

[anewton1998]

I don't understand the use case. What does it mean? If the value is not there then assume a default value? Why would a validator care? I think for XSD and JSON Schema, the want to address instances where tool chains are generating code. Is that where we want to go?

[codalogic]

For the use-case...

In YANG (imagine it's actually JSON!), the leaf rule has an optional mandatory member saying whether the leaf is required or not in an instance:

leaf name {
    type string;
    description "Name of the product.";
    mandatory true;
}

If defined in JCR, the definition would be:

"mandatory" : boolean ?

But the question is, what happens when mandatory is absent? Should the leaf be present or not? Doing something similar to:

"mandatory" : @{default false} boolean ?

let's the spec reader and implementer readily know what the semantics are without having to scan through the text.

The following might also work:

"mandatory" : boolean ?, ; default: false

I agree that a validator wouldn't benefit from it, but I think humans might.

That said, I think we can wait on this one if we think there are more important things.

[anewton1998]

Ok. As long as we are clear that is really for humans and not validators, I'm good with it. Your annotation approach is my preference.