In his note entitled "XML Notation Schemas", Rick pointed out "two severely broken non-conformances", namely: - supporting non-well-formed XML 1.0; - treating namespace URIs as schema names. I believe that Rick is right. One of the ideas he suggested is the use of XSL patterns for describing schemata. >Using XSL as a Structure Validation Language, which characterizes document >validation as as stylesheet issue and points out that XSL's pattern language >allows validation on very different criteria to SGML's content model approach; If we allow non-terminals in the schema language, we can construct a schema from an XSL pattern (probably, with some restriction). A document is valid against this constructed schema if and only if some element in this document matches the given pattern. Formally speaking, a pattern can be captured by a pair of tree regular expression (conditions on subordinates) and pointed tree regular expression (conditions on non-subordinates such as superiors, siblings, etc). Kleene's theorem ensures the construction of a tree regular grammar from a tree regular expression. My work (PODP'96) allows for the construction of unambiguous non-determinstic tree automaton from a pointed tree regular expression. We then remove matching states from this unambiguous automaton. By applying, subset construction and negation, we can construct a tree regular grammar that mimicks the pointed tree regular expression. Makoto Fuji Xerox Information Systems Tel: +81-44-812-7230 Fax: +81-44-812-7231 E-mail: murata@apsdc.ksp.fujixerox.co.jpReceived on Sunday, 23 May 1999 23:52:24 UTC
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