What YAML is
YAML uses indentation instead of brackets. It is a superset of JSON, supports comments, and is meant to be edited by hand.
Kubernetes manifests, CI pipelines, Ansible playbooks and most modern config files.
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 changes when you convert YAML to XML
A YAML list of maps reads as rows and columns directly. Anchors and aliases are resolved before the table is built, so a repeated block arrives expanded rather than as a reference.
Each row becomes an element with one child per column. Header names are rewritten where they have to be, because an XML tag cannot start with a digit or contain a space, so a column called 2024 Sales becomes _2024_Sales.
What carries over from YAML to XML
YAML records 2 things about a table that XML has no way to hold.
YAML distinguishes a number from the text of a number; XML does not, so every value arrives as text and has to be re-parsed by whatever reads it next.
An empty cell and a missing one are the same thing in XML, so a null and an empty string in the YAML both come out blank and can no longer be told apart.
The identifier 007 comes out of the XML 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 XML file goes wrong.
The quotes around Jonah "Jo" Pryce are written as the HTML entity " in the XML.