Guides

The parts of XML that trip people up, explained at the level a working engineer needs. Each one cites the specification it is describing, and links to the tool that does the thing.

• Well-formed versus valid XMLTwo different checks that almost every tool conflates.
• XML versus JSONA comparison written for people who have to choose, not to declare a winner.
• What is an XSD?XML Schema from the ground up, including which version your tools support.
• DTD versus XSDThe comparison, plus where DTDs are still genuinely used.
• XML namespaces, demystifiedWhy the prefix does not matter and the default namespace breaks XPath.
• XPath, from scratchPaths, predicates and the namespace handling every tutorial skips.
• XSLT basicsTemplate matching, and the namespace mistake that produces an empty result.
• Chrome is removing XSLTThe dates, what breaks, and the four ways out.
• XML security risksXXE, entity expansion, and the exact flag to set in each language.
• The billion laughs attackA kilobyte that expands to a gigabyte, and the defence in four languages.
• The XML declaration and encodingWhy the declaration is a claim about bytes, and how a BOM breaks things.
• CDATA sectionsWhat CDATA does not do, and when to escape instead.
• Converting XML to JSONWhy every converter gives a different answer, and how to pick one.
• XML sitemaps that actually workThe limits, the lastmod rule, and what Google has said it ignores.
• RSS and Atom feed structureWhat each format requires, and the mistakes that break real feeds.