Abstract not found

A permutation phrase is a sequence of elements (possibly of di#erent types) in which each element occurs exactly once and the order is irrelevant. Some of the permutable elements may be optional. We show a way to extend a parser combinator library with support for parsing such free-order constructs. A user of the library can easily write parsers for permutation phrases and does not need to care about checking and reordering the recognised elements. Possible applications include the generation of parsers for attributes of XML tags and Haskell's record syntax.

We take the term X/O impedance mismatch to describe the difficulty of the OO paradigm to accommodate XML processing by means of recasting it to typed OO programming. In particular, given XML types (say, XML schemas), it is notoriously difficult to map them automatically to object types (say, object models) that (i) reasonably compare to native object types typically devised by OO developers; (ii) fully preserve the intent of the original XML types; (iii) fully support round-tripping of arbitrary, valid XML data; and (iv) provide a general and convenient programming model for XML data hosted by objects. We reveal the X/O impedance mismatch in particular detail. That is, we survey the relevant differences between XML and objects in terms of their data models and their type systems. In this process, we systematically record and assess Xto-O mapping options. Our illustrations employ XSD (1.0) as the XML-schema language of choice and C# (1.0–3.0) as the bound of OO language expressiveness.

We introduce a fifth language accepting machine called the PDA-T, demonstrate some of its interesting formal properties, and show its role in the $-Calculus( Based upon this new machine and the $-Calculus' other properties, we demonstrate the $-Calculus' formal Turing Power, and then propose a formal language classification (the $-Hierarchy), derived largely from the Chomsky Hierarchy, but with a fifth class of language accepted by the PDA-T. We show that this modified hierarchy yields several conceptual benefits over the standard four machine Chomsky Hierarchy. We also provide some practical examples of the use of $-grammars in contextsensitive and semantic parsing.

This report is the first of a two part series in which we address fundamental design issues in the syntax of programming languages and the way in which implementation difficulties have had a deleterious effect on the expresiveness of languages. We

A permutation phrase is a sequence of elements (possibly of different types) in which each element occurs exactly once and the order is irrelevant. Some of the permutable elements may be optional. We show a way to extend a parser combinator library with support for parsing such free-order constructs. A user of the library can easily write parsers for permutation phrases and does not need to care about checking and reordering the recognised elements. Possible applications include the generation of parsers for attributes of XML tags and Haskell's record syntax.

We examine the usefulness of the Meta-S Calculus as a formalism for natural language parsing, and in particular the power of a single adaptive predicate in a structure-only English grammar in providing document wide context resolution. We were able to construct an Meta-S grammar for a limited subset of English that a) contained no English words at start, and b) correctly parsed a series of twenty-two sentences without the use of any mechanism outside the formalism of the Meta-S grammar itself.