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Answers about the query engine and its limits, how the AI features work, and what happens to the documents you paste. The answers themselves are on the page — this summary exists so search engines can find the questions.
XML Foundry evaluates queries with FontoXPath, a pure-JavaScript XPath 3.1 and XQuery 3.1 engine that runs entirely in your browser. Queries are never sent to a server. XSLT (fn:transform), updating expressions, and XQuery modules are outside the engine's scope; the reference lists each unsupported construct with a portable rewrite.
Which engine powers XML Foundry? · XPath 1.0 vs 3.1 · How complete is XQuery support? · Engine support and limits
The AI helpers — plain-English explanations, diagnostics for a failing query, optimization suggestions, and generated practice tasks — are optional and rate-limited. Progress is stored locally for anonymous visitors and synced to your account once you sign in.
How do the AI features work? · What data is stored? · Privacy policy · Licenses