JSON

Disclaimer: for now it's C# only

The following JSON format can be ingested into VW:

• Top-level properties are considered features for the default namespace.
• Top-level non-features are considered namespaces.
• Features are JSON strings, integer, float, boolean, arrays of integers and/or floats.
• Top-level properties starting with _ are ignored, except if they match a special property (e.g. "_label").
• Labels can be passed using top-level "_label" property.
• If the JSON value is either a string, integer or float is converted to a string and passed directly to VW label parser.
• If the JSON value is an object, the first property needs to match one of the JSON properties of SimpleLabel or ContextualBanditLabel.

The C# layer can ingest

• JSON strings
• JSON.NET's JsonReader
• C# objects serializable to the above JSON format using JSON.NET serializing rules. Thus JsonProperty annotations are inspected and so on. This is particularly useful if one needs to score a given object, then serialize it JSON and train from the JSON serialization as it circumvents the de-serialization for the scoring part.

Examples

JSON	VW String
{"f1":25,"f2":true,"_aux":"some ignored info"}	| f1:25 f2
{"ns1":{"location":"New York"},"f2":[1,0.2,3]}	|ns1 New_York | :1 :.2 :.3
{"ns1":{"location":"New York"},"ns2":{"f2":3.4},"_label":1}	1 |ns1 New_York |ns2 f2:3.4
{"ns1":{"location":"New York", "f2":3.4},"_label":{"Label":2,"Weight":0.3}}	2 0.3 |ns1 New_York f2:3.4