What XML is
XML marks up data with nested named tags and optional attributes. It is verbose, strict about being well-formed, and can carry a schema that says what shape a document must have.
Enterprise integrations, government data feeds, RSS, SOAP services and older document formats.
What TOML is
TOML is a configuration format with explicit types and a table syntax, designed to be unambiguous where YAML is clever.
Rust and Python projects, and anything with a pyproject.toml or Cargo.toml.
What changes when you convert XML to TOML
The first repeating element is treated as the rows. Attributes are read alongside child elements and prefixed so they do not collide with a same-named tag. Nesting one level deep becomes dotted column names; deeper structures are kept as text.
Each row becomes an entry in an array of tables. Keys are sanitised to bare keys where possible and quoted where not.
What carries over from XML to TOML
XML records 2 things about a table that TOML has no way to hold.
TOML wants a type for each column, and XML does not record one, so each column is typed from what its values look like. A column of digits that should stay text - a zip code, a phone number, a leading-zero id - is the usual thing to check afterwards.
An empty cell and a missing one are the same thing in TOML, so a null and an empty string in the XML both come out blank and can no longer be told apart.
XML can hold a value that is itself a list or an object. TOML has only flat cells, so nested values are flattened into one cell rather than being spread across columns.
The identifier 007 comes out of the TOML as 007. Reading it as a number would have made it 7, and an id that changes value is worse than one that stays text.
The role "Analyst, data" survives with its comma, in one cell rather than split across two. That is the first thing to check in any converted table, and the usual place a TOML file goes wrong.
The quotes around Jonah "Jo" Pryce are escaped with a backslash in the TOML.