In previous work we studied a new type of DCGs, Datalog grammars, which are inspired on database theory. Their efficiency was shown to be better than that of their DCG counterparts under (terminating) OLDT-resolution. In this article we motivate a variant of Datalog grammars which allows us a meta-grammatical treatment of coordination. This treatment improves in some respects over previous work on coordination in logic grammars, although more research is needed for testing it in other respects.
a) neither method formulates exactly how parallelism is to be determined- it is just postulated as a prerequisite to the resolution of ellipsis (although @cite_6 speculates on possible ways of formulating this, leaving it for future work)
@cite_6
2168671000 2139801570 2115755647 1999281702
This paper reports on an empirically based system that automatically resolves VP ellipsis in the 644 examples identified in the parsed Penn Treebank. The results reported here represent the first systematic corpus-based study of VP ellipsis resolution, and the performance of the system is comparable to the best existing systems for pronoun resolution. The methodology and utilities described can be applied to other discourse-processing problems, such as other forms of ellipsis and anaphora resolution.The system determines potential antecedents for ellipsis by applying syntactic constraints, and these antecedents are ranked by combining structural and discourse preference factors such as recency, clausal relations, and parallelism. The system is evaluated by comparing its output to the choices of human coders. The system achieves a success rate of 94.8 , where success is defined as sharing of a head between the system choice and the coder choice, while a baseline recency-based scheme achieves a success rate of 75.0 by this measure. Other criteria for success are also examined. When success is defined as an exact, word-for-word match with the coder choice, the system performs with 76.0 accuracy, and the baseline approach achieves only 14.6 accuracy. Analysis of the individual components of the system shows that each of the structural and discourse constraints used are strong predictors of the antecedent of VP ellipsis. We consider parallel algorithms working in sequential global time, for example, circuits or parallel random access machines (PRAMs). Parallel abstract state machines (parallel ASMs) are such parallel algorithms, and the parallel ASM thesis asserts that every parallel algorithm is behaviorally equivalent to a parallel ASM. In an earlier article, we axiomatized parallel algorithms, proved the ASM thesis, and proved that every parallel ASM satisfies the axioms. It turned out that we were too timid in formulating the axioms; they did not allow a parallel algorithm to create components on the fly. This restriction did not hinder us from proving that the usual parallel models, like circuits or PRAMs or even alternating Turing machines, satisfy the postulates. But it resulted in an error in our attempt to prove that parallel ASMs always satisfy the postulates. To correct the error, we liberalize our axioms and allow on-the-fly creation of new parallel components. We believe that the improved axioms accurately express what parallel algorithms ought to be. We prove the parallel thesis for the new, corrected notion of parallel algorithms, and we check that parallel ASMs satisfy the new axioms. There have been a number of recent papers on aligning parallel texts at the sentence level, e.g., (1991), Gale and Church (to appear), Isabelle (1992), Kay and Rosenschein (to appear), (1992), Warwick-Armstrong and Russell (1990). On clean inputs, such as the Canadian Hansards, these methods have been very successful (at least 96 correct by sentence). Unfortunately, if the input is noisy (due to OCR and or unknown markup conventions), then these methods tend to break down because the noise can make it difficult to find paragraph boundaries, let alone sentences. This paper describes a new program, char_align, that aligns texts at the character level rather than at the sentence paragraph level, based on the cognate approach proposed by Abstract This paper presents some fundamental properties of independent and- parallelism and extends its applicability by enlarging the class of goals eligible for parallel execution. A simple model of (independent) and-parallel execution is proposed and issues of correctness and efficiency are discussed in the light of this model. Two conditions, “strict” and “nonstrict” independence, are defined and then proved sufficient to ensure correctness and efficiency of parallel execution: If goals which meet these conditions are executed in parallel, the solutions obtained are the same as those produced by standard sequential execution. Also, in the absence of failure, the parallel proof procedure does not generate any additional work (with respect to standard SLD resolution), while the actual execution time is reduced. Finally, in case of failure of any of the goals, no slowdown will occur. For strict independence, the results are shown to hold independently of whether the parallel goals execute in the same environment or in separate environments. In addition, a formal basis is given for the automatic compile-time generation of independent and-parallelism: Compiletime conditions to efficiently check goal independence at run time are proposed and proved sufficient. Also, rules are given for constructing simpler conditions if information regarding the binding context of the goals to be executed in parallel is available to the compiler.