The extensibility, flexibility, expressiveness, and platform-neutrality of XML delivers key advantages for interoperability. The interoperability of XML Web services often comes at the price of reduced efficiency of message composition, transfer, and parsing compared to simple binary protocols. This paper presents a high-performance XML parsing and validation technique that is time and space optimal. A schema-specific parsing method is developed that uses a two-stack push-down automaton (PDA) for single-pass parsing and validation without backtracking. The schema validity constraints are packed in a compact parsing table derived from a permutation phrase grammar. This approach reduces both the space and time requirements of XML parsing and validation. By contrast, other XML schema-specific parsing methods trade efficiency for space (larger code and/or data size) or trade space for efficiency (backtracking). Performance results show that the method is significantly faster than traditional validating and non-validating XML parsers.
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