XMLYAML

XMLYAML is a proposed data interchange format that seeks to combine XML’s hierarchical, attribute-rich model with YAML’s human-friendly syntax. It aims to allow data to be serialized into a form that remains compatible with XML-aware workflows while being easier for humans to read and edit. There is no widely adopted standard for XMLYAML, and existing implementations are mainly experimental or targeted at specific toolchains.

Its design centers on mapping XML constructs to YAML equivalents. Elements are represented as mappings or sequences, attributes are usually represented as keys prefixed with a marker such as @, and namespaces can be preserved as dedicated fields. Text content in mixed-content elements may be stored under a key such as text, while repeated child elements become lists. The approach seeks to be lossless when designed carefully, though some schemas may choose to preserve only the information required for a given use case.

An illustrative conversion can help clarify the idea. Consider the XML:

<person id="123" xmlns="http://example.org">

<name>Alex</name>

<phones>

<phone type="mobile">555-1234</phone>

<phone type="work">555-5678</phone>

</phones>

</person>

A corresponding XMLYAML representation might be:

person:

@id: '123'

xmlns: 'http://example.org'

name: Alex

phones:

- @type: mobile

text: 555-1234

- @type: work

text: 555-5678

Adoption and tooling for XMLYAML remain limited. Some projects explore it to bridge XML-based data stores with YAML-driven configuration or scripting workflows, while others view it as a niche interop approach that requires careful schema mapping. Potential advantages include improved human readability and easier editing, whereas challenges include preserving all XML features (such as complex namespaces and mixed content) and ensuring lossless round-tripping across diverse implementations.