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There are many aspects of XML that require knowledge of its context. For example, earlier in the week my “XML quiz” noted that & does not always mean & (in the context of a CDATA section or a comment it means & but otherwise it
means &) So things are context-dependent. Another way of saying it is: Things are context-sensitive. XML is context-sensitive. Koan: If XML isn’t context-free, why are we always writing context-free grammars for it? (And don't say, "Because it's useful to do so;" that begs the question:
Why is it useful?) Scroll down to see the answer ………….. Even though XML isn’t context-free as such, it is
locally context-free, in the sense that the set of permissible expressions within a small region in a particular XML document can be described by a context-free grammar. Adapted from the article “The Concept of Grammar Adaptability” by John N. Shutt (https://web.cs.wpi.edu/~jshutt/adapt/concept.html) |