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This paper describes a probabilistic top-down parser for minimalist grammars. Top-down parsers have the great advantage of having a certain predictive power during the parsing, which takes place in a left-to-right reading of the sentence.…

Computation and Language · Computer Science 2010-10-12 Thomas Mainguy

Regular expressions with backreferences (regex, for short), as supported by most modern libraries for regular expression matching, have an NP-complete matching problem. We define a complexity parameter of regex, called active variable…

Formal Languages and Automata Theory · Computer Science 2024-02-09 Markus L. Schmid

Error recovery is an essential feature for a parser that should be plugged in Integrated Development Environments (IDEs), which must build Abstract Syntax Trees (ASTs) even for syntactically invalid programs in order to offer features such…

Programming Languages · Computer Science 2025-07-08 Sérgio Queiroz de Medeiros , Fabio Mascarenhas

We present the squirrel parser, a PEG packrat parser that directly handles all forms of left recursion with optimal error recovery, while maintaining linear time complexity in the length of the input even in the presence of an arbitrary…

Programming Languages · Computer Science 2026-01-09 Luke A. D. Hutchison

Hyperedge replacement (HR) grammars can generate NP-complete graph languages, which makes parsing hard even for fixed HR languages. Therefore, we study predictive shift-reduce (PSR) parsing that yields efficient parsers for a subclass of HR…

Formal Languages and Automata Theory · Computer Science 2019-03-12 Frank Drewes , Berthold Hoffmann , Mark Minas

Incorporating external knowledge bases in traditional retrieval-augmented generation (RAG) relies on parsing the document, followed by querying a language model with the parsed information via in-context learning. While effective for…

Computation and Language · Computer Science 2026-02-03 Jacob Si , Mike Qu , Michelle Lee , Marek Rei , Yingzhen Li

We study the computational power of parsing expression grammars (PEGs). We begin by constructing PEGs with unexpected behaviour, and surprising new examples of languages with PEGs, including the language of palindromes whose length is a…

Formal Languages and Automata Theory · Computer Science 2020-02-17 Bruno Loff , Nelma Moreira , Rogério Reis

Sequence tagging models for constituent parsing are faster, but less accurate than other types of parsers. In this work, we address the following weaknesses of such constituent parsers: (a) high error rates around closing brackets of long…

Computation and Language · Computer Science 2019-10-15 David Vilares , Mostafa Abdou , Anders Søgaard

This paper presents an extension of the GLL parsing algorithm for context-free grammars which also supports parsing expression grammars with ordered choice and lookahead. The new PEGLL algorithm retains support for unordered choice, and…

Formal Languages and Automata Theory · Computer Science 2022-08-29 Aaron Moss , Brynn Harrington , Emily Hoppe

Regular expression (regex) matching is fundamental in many applications, especially in web services. However, matching by backtracking -- preferred by most real-world implementations for its practical performance and backward compatibility…

Programming Languages · Computer Science 2024-02-02 Hiroya Fujinami , Ichiro Hasuo

Referring expression generation (REG) algorithms offer computational models of the production of referring expressions. In earlier work, a corpus of referring expressions (REs) in Mandarin was introduced. In the present paper, we annotate…

Computation and Language · Computer Science 2021-08-17 Guanyi Chen , Kees van Deemter

Nez is a PEG(Parsing Expressing Grammar)-based open grammar language that allows us to describe complex syntax constructs without action code. Since open grammars are declarative and free from a host programming language of parsers,…

Programming Languages · Computer Science 2015-11-30 Kimio Kuramitsu

Retrieval-Augmented Generation (RAG) enhances language models by retrieving and incorporating relevant external knowledge. However, traditional retrieve-and-generate processes may not be optimized for real-world scenarios, where queries…

Computation and Language · Computer Science 2025-02-28 Ingeol Baek , Hwan Chang , Byeongjeong Kim , Jimin Lee , Hwanhee Lee

This paper describes the functioning of a broad-coverage probabilistic top-down parser, and its application to the problem of language modeling for speech recognition. The paper first introduces key notions in language modeling and…

Computation and Language · Computer Science 2007-05-23 Brian Roark

I introduce a formalism for representing the syntax of recursively structured graph-like patterns. It does not use production rules, like a conventional graph grammar, but represents the syntactic structure in a more direct and declarative…

Formal Languages and Automata Theory · Computer Science 2025-04-25 Peter Fletcher

Retrieval-augmented generation (RAG) systems have been shown to be effective in addressing many of the drawbacks of relying solely on the parametric memory of large language models. Recent work has demonstrated that RAG systems can be…

We introduce AccurateRAG -- a novel framework for constructing high-performance question-answering applications based on retrieval-augmented generation (RAG). Our framework offers a pipeline for development efficiency with tools for raw…

Computation and Language · Computer Science 2026-03-04 Linh The Nguyen , Chi Tran , Dung Ngoc Nguyen , Van-Cuong Pham , Hoang Ngo , Dat Quoc Nguyen

Current efficient fine-tuning methods (e.g., adapters, prefix-tuning, etc.) have optimized conditional text generation via training a small set of extra parameters of the neural language model, while freezing the rest for efficiency. While…

Computation and Language · Computer Science 2022-05-24 Marjan Ghazvininejad , Vladimir Karpukhin , Vera Gor , Asli Celikyilmaz

Retrieval-augmented generation (RAG) ranks passages by semantic similarity to the input, implicitly assuming that semantic similarity is a reliable indication of applicability in downstream tasks. This assumption breaks down when task…

Information Retrieval · Computer Science 2026-05-28 Zhixing Sun , Shenghe Xu , Tao Li

Retrieval-Augmented Generation (RAG) has been proposed to mitigate hallucinations in large language models (LLMs), where generated outputs may be factually incorrect. However, existing RAG approaches predominantly rely on vector similarity…

Information Retrieval · Computer Science 2026-04-28 Miao Xie , Xiao Zhang , Yi Li , Chunli Lv