Object Data Instance Notation - ODIN library
In the openEHR (EHR = Electronic Health Record) project, we use a serialisation that is called ODIN, an alternative to JSON, XML etc. It was developed before JSON existed, and is more comprehensive (particularly in terms of leaf types). It is also (in my view) easier to read. It's certainly easier to write (in JSON,  and "" will eventually drive you crazy). You can read about it here.
This library is currently used for:
- application .cfg files
- multi-lingual error messages
- object model schemas (i.e. as a replacement for XMI)
- to express direct serialisations of object structures in other programming artefacts
The library consists of:
- parser and serialiser
- DT (data tree) library - intermediate DOM-like representation
- DT <=> object bidirectional data converter
- Xpath-like path functionality on the data tree
It is implemented in a number of languages.
I have often wondered if it could become a de facto serialisation for use with Eiffel, since none of the other formats in use are very friendly (data serialisation, XML .ecf files), and there is no standard format at all for multi-lingual error and UI messages.