A Kotlin reference implementation of the Ion Schema Specification. This is currently alpha software and all aspects of it are subject to change.
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Ion Schema Kotlin

A reference implementation of the Ion Schema Specification, written in Kotlin.

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This is currently alpha software and all aspects of it are subject to change.

Getting Started

The following code provides a simple example of how to use this API from Java. The Customer type is a struct that requires firstName and lastName fields as strings, while the middleName field is optional.

Before running, replace <base_path> with the path containing "/data/test".

import software.amazon.ion.IonSystem;
import software.amazon.ion.IonValue;
import software.amazon.ion.system.IonSystemBuilder;
import software.amazon.ionschema.AuthorityFilesystem;
import software.amazon.ionschema.IonSchemaSystem;
import software.amazon.ionschema.Schema;
import software.amazon.ionschema.Type;

public class IonSchemaGettingStarted {
    private static IonSystem ION = IonSystemBuilder.standard().build();

    public static void main(String[] args) {
        IonSchemaSystem iss = IonSchemaSystem.Builder.standard()
                .withAuthority(new AuthorityFilesystem("<base_path>/data/test"))

        Schema schema = iss.loadSchema("/schema/Customer.isl");
        Type type = schema.getType("Customer");

        checkValue(type, "{ firstName: \"Susie\", }");
        checkValue(type, "{ firstName: \"Susie\", lastName: \"Smith\" }");
        checkValue(type, "{ firstName: \"Susie\", middleName: \"B\", lastName: \"Smith\" }");

    private static void checkValue(Type type, String str) {
        IonValue value = ION.singleValue(str);
        System.out.println(str + ": " + type.isValid(value));

Helping out

The issues identified below represent the next steps for this project. Most are relatively small and self-contained; larger efforts are shown below in bold.

  • #1 add/verify support for schema import
  • #2 provide validation details when a value is invalid
  • #3 add support for open/closed content
  • #4 implement the annotations constraint
  • #5 implement the timestamp_offset constraint
  • #6 implement the timestamp_precision constraint
  • #7 verify the element constraint works for structs
  • #8 update valid_values constraint to support timestamp ranges
  • #9 assert that constraints are compatible with the type on which they are specified
  • #10 define a schema for ISL
  • #11 add support for the document type


This library is licensed under the Apache 2.0 License.