YAMLin

YAMLin is a data-serialization language that extends YAML with a formal schema system, aiming to improve correctness and interoperability in configuration and data exchange. Conceived as an evolution of YAML 1.2, YAMLin keeps the human-readable syntax while introducing typed values, modular composition, and explicit validation rules.

The syntax of YAMLin remains indentation-based and readable, maintaining YAML’s mappings, sequences, and scalars. It adds an optional type layer, allowing values to be annotated with primitive and composite types, and introduces a separate YAMLin Schema language to declare valid shapes for documents. Import mechanisms enable modular configuration by referencing external YAMLin files.

Key features include static typing through the schema language, runtime validation during parsing, and controlled merging of imports to avoid unpredictable results. YAMLin also provides anchors and aliases with deterministic resolution rules, and a restricted evaluation model that avoids arbitrary code execution for security.

Tooling and implementations exist across multiple programming languages. Reference parsers validate documents against schemas, and there are editors and linters designed to fit into existing DevOps pipelines. Several projects report improved maintainability and early error detection in large configurations when adopting YAMLin.

YAMLin is used mainly for configuration management, deployment manifests, and data interchange in distributed systems. While it is still developing, some organizations experiment with YAMLin where typed validation and modular composition outweigh the need to maintain plain YAML.