[Ajedi32]

For configuration I dislike the XML object model KDL is built around. It needlessly complicates things to have two different incompatible ways (properties and children) of nesting configuration keys under an element.

Pkl seems syntactically beautiful and powerful, but having types and functions and loops makes it a lot more complicated than the dead-simple JSON data model that YAML is based on.

[speed_spread]

In JSON I often end up recreating XML attributes equivalent for metadata fields and using custom prefixes to differentiate those fields from actual data. I find it's nice the data/metadata separation at the language level.

[Ajedi32]

Can you give an example of metadata you would put in a config file that isn't configuration and isn't a comment?

[speed_spread]

Metadata is less useful in a config file since it's all static data. But for something more dynamic (messaging, persistence) attributes can be used for Time-To-Live, object class, source, signature, etc.