schema/

    Although KEKS can be decoded without any schema definition/specification,
    data structures are likely to be checked against some kind of the schema.
    Here is suggestion (not a requirement!) to use relatively simple data
    structure validation specifications/schemas.

    How are data structures checked? You check if they have required fields,
    have necessary types of fields, satisfying lengths of the lists/maps or
    strings, and so on. In most cases those checks covers nearly everything
    when you sanitise the structures.

    So suggestion is to specify those steps for some kind of the
    interpreter, that executes validation commands ([schema/cmds]) against
    the provided data structures. That interpreter should be simple enough
    to be able to implement it quickly and with sane amount of code.
    Validation steps should be easily decodable and conveniently parsed even
    in C-language.

    Let's use KEKS format itself for the serialised validation steps! And
    generate them from higher level language/code ([schema/tcl]), convenient
    for humans.

        [schema/tcl] -> [schema/cmds] -> keks-encode() => schema
        validate(schema, data)