README

TypeScript Interfaces describing the Keras JSON format

This directory contains a description of the current Keras JSON serialization format, in the form of TypeScript interfaces. The intent is that any valid Keras JSON file can be parsed in a type-safe manner using these types.

The Keras JSON format originated in the Python Keras implementation. The basic design is that the format mirrors the Python API. Each class instance in a Python model is serialized as a JSON object containing the class name and its serialized constructor arguments.

Here, we provide a type called *Serialization to describe the on-disk JSON representation for each class. It always provides a class_name and a config representing the constructor arguments required to reconstruct a given instance.

The constructor arguments may be primitives, arrays of primitives, or plain key-value dictionaries, in which case the JSON serialization is straightforward.

If a constructor argument is another object, then it is represented by a nested *Serialization. This structure is illustrated below:

FooSerialization {
  class_name: 'Foo';
  config: {
    bar: string;
    baz: number[];
    qux: QuxSerialization;
  }
}

Deserializing such a nested object configuration requires recursively deserializing any object arguments, and finally calling the top-level constructor using the reconstructed object arguments.

In general this means that deserialization is purely tree-like, so instances cannot be reused. (The deserialization code for Models is an exception to this principle, because it allows Layers to refer to each other in order to describe a DAG).

As a consequence of this design, our deserialization code requires an *Args type mirroring each of the *Serialization types here. *Args types represent the actual arguments passed to a constructor, after any nested objects have been deserialized. For instance, the above FooSerialization will be resolved into FooArgs like this:

 FooArgs {
   bar: string;
   baz: number[];
   qux: Qux;
 }

which can then be passed to the Foo constructor.