Ion (serialization format)
# Ion (serialization format)

Ion is a data serialization language developed by Amazon. It may be represented by either a human-readable text form or a compact binary form. The text form is a superset of JSON; thus, any valid JSON document is also a valid Ion document.

## Data types

As a superset of JSON, Ion includes the following data types

* null: An empty value
* bool: Boolean values
* string: Unicode text literals
* list: Ordered heterogeneous collection of Ion values
* struct: Unordered collection of key/value pairs

The nebulous JSON 'number' type is strictly defined in Ion to be one of

* int: Signed integers of arbitrary size
* float: 64-bit IEEE binary-encoded floating point numbers
* decimal: Decimal-encoded real numbers of arbitrary precision

Ion adds these types:

* timestamp: Date/time/time zone moments of arbitrary precision
* symbol: Unicode symbolic atoms (aka identifiers)
* blob: Binary data of user-defined encoding
* clob: Text data of user-defined encoding
* sexp: Ordered collections of values with application-defined semantics

Each Ion type supports a null variant, indicating a lack of value while maintaining a strict type (e.g., null.int, null.struct).

The Ion format permits annotations to any value in the form of symbols. Such annotations may be used as metadata for otherwise opaque data (such as a blob).

## Implementations

* Amazon supported library implementations
* C#
* Go Lang
* Python
* JS

## Examples

### Uses

* Amazon's Quantum Ledger Database (QLDB) stores data in Ion documents.
* PartiQL, an open source SQL-based query language also by Amazon, is built upon Ion. PartiQL supported queries are used by QLDB, S3Select.

## Tooling and extensions

* Ion Path Extractor API aims to combine the convenience of a DOM API with the speed of a streaming API.
* IDE support
   * Eclipse
   * IntelliJ
* Jackson data format module for Ion
* Apache Hive SerDe for Ion
* Ion Schema
   * Specification
   * Implementations
* Ion Hash defines an algorithm for constructing a hash for any Ion value.
   * Specification
   * Implementations
