[jcelerier]

i'd much rather have

    [ { line: [10, 10] }, { cubic: [ 5, 15, 15, 5 ] }, ... ] 

or even

    [ ["line", 10, 10], ["cubic", ...], ... ] 

- anything as long as there's a way to stream the data (which is not possible with your format as you need to receive the whole object before being able to do anything).

[afiori]

this makes me realize that xml maps relatively well to JSON array whose elements are object with 1 fields (or 2 fields) whose value is again a similar array.