XML (Extensible Markup Language)
XML is the W3C markup language for structured documents — elements, attributes, namespaces — that underpins standards from ISO 20022 payment files and SCORM manifests to SOAP services, XSD schemas, and sitemaps.
The rules that matter
Well-formedness is strict: every element closes, attributes are quoted, exactly one root, tags nest properly, and the language is case-sensitive. Namespaces disambiguate vocabularies — xmlns="urn:iso:std:iso:20022:tech:xsd:pain.001.001.03" both identifies the message type and tells a validator which schema version applies. An XML declaration can state encoding; UTF-8 is the modern default.
Schema validation layers on top: XSD defines which elements and attributes may appear, their order, cardinality, and datatypes — the mechanism banks use to reject malformed pain.001 files before processing.
Where it still dominates
JSON won the web-API war, but XML remains the language of regulated interchange: ISO 20022 financial messages, e-invoicing, SCORM package manifests, SAML assertions, SOAP enterprise services, and sitemaps are all XML. That is why we maintain a full XML toolkit — formatter, validator, XSD validation, XPath testing, and conversion to JSON and CSV.
Related Standards
- •XML 1.0/1.1 — W3C recommendation
- •XML Schema (XSD) — W3C
- •XPath — W3C query language
Free Tools & Resources
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