Repeating $ vs repeating Shape

[cecilemuller]

A question from the X3D mailing-list referencing #1 :

Wondering then, what about your repeated use of "$", isn't that the same sort of repetition as repeating "Shape" and "Transform" ?

(Edit: $ used to be called _type at the time)

[cecilemuller]

The main difference is that using Shape as object property adds one extra nesting level.
Let's take a list of three shapes for example.

Using Shape as property, it needs three levels:

[
    {
        "Shape": {
            ...
        }
    },
    {
        "Shape": {
            ...
        }
    },
    {
        "Shape": {
            ...
        }
    }
]

because you can't do this given key/value pairs implies an Object, not an Array:

[
    "Shape": {
        ...
    },
    "Shape": {
        ...
    },
    "Shape": {
        ...
    }
]

and you can't do this either (c.f. #2 ):

{
    "Shape": {
        ...
    },
    "Shape": {
        ...
    },
    "Shape": {
        ...
    }
}

---

The same list using $ only needs two levels:

[
    {
        "$": "Shape"
        ...
    },
    {
        "$": "Shape"
        ...
    },
    {
        "$": "Shape"
        ...
    }
]