Double Greibach operator grammars

AbstractEvery context-free grammar can be transformed into one in double Greibach operator form, that satisfies both double Greibach form and operator form. Examination of the expressive power of various well-known subclasses of context-free grammars in double Greibach and/or operator form yields an extended hierarchy of language classes. Basic decision properties such as equivalence can be stated in stronger forms via new classes of languages in this hierarchy

An evaluation of Lolita and related natural language processing systems

This research addresses the question, "how do we evaluate systems like LOLITA?" LOLITA is the Natural Language Processing (NLP) system under development at the University of Durham. It is intended as a platform for building NL applications. We are therefore interested in questions of evaluation for such general NLP systems. The thesis has two, parts. The first, and main, part concerns the participation of LOLITA in the Sixth Message Understanding Conference (MUC-6). The MUC-relevant portion of LOLITA is described in detail. The adaptation of LOLITA for MUC-6 is discussed, including work undertaken by the author. Performance on a specimen article is analysed qualitatively, and in detail, with anonymous comparisons to competitors' output. We also examine current LOLITA performance. A template comparison tool was implemented to aid these analyses. The overall scores are then considered. A methodology for analysis is discussed, and a comparison made with current scores. The comparison tool is used to analyse how systems performed relative to each-other. One method, Correctness Analysis, was particularly interesting. It provides a characterisation of task difficulty, and indicates how systems approached a task. Finally, MUC-6 is analysed. In particular, we consider the methodology and ways of interpreting the results. Several criticisms of MUC-6 are made, along with suggestions for future MUC-style events. The second part considers evaluation from the point of view of general systems. A literature review shows a lack of serious work on this aspect of evaluation. A first principles discussion of evaluation, starting from a view of NL systems as a particular kind of software, raises several interesting points for single task evaluation. No evaluations could be suggested for general systems; their value was seen as primarily economic. That is, we are unable to analyse their linguistic capability directly

LIPIcs, Volume 274, ESA 2023, Complete Volume

LIPIcs, Volume 274, ESA 2023, Complete Volum

Programming Languages and Systems

This open access book constitutes the proceedings of the 30th European Symposium on Programming, ESOP 2021, which was held during March 27 until April 1, 2021, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2021. The conference was planned to take place in Luxembourg and changed to an online format due to the COVID-19 pandemic. The 24 papers included in this volume were carefully reviewed and selected from 79 submissions. They deal with fundamental issues in the specification, design, analysis, and implementation of programming languages and systems

Access in a global rattan production network: a case study of rattan originating from Central Sulawesi, Indonesia and upgraded for sale in international markets

Forests and forest users are increasingly engaged in global scale markets that connect different stages of commodity production and retail. This thesis adopts a Global Production Network framing in order to investigate the case of rattan cane and furniture. I examine the ways in which actors benefit from rattan (a non-timber forest product) and elucidate power dynamics that explain how some actors are better positioned to benefit from rattan than others. My conceptual framework combines the literature on access with global production networks. I explore access starting in the forests of Sulawesi, Indonesia, moving to processing in larger centres in Sulawesi and Java, and ending in retail shops in the UK. This approach enables an analysis of rich mixed-method empirical data. My main findings centre around Indonesia’s rattan export ban, which benefited only elites and served to support the overall decline of global rattan furniture markets. Further, I elucidate the influence that access at one phase of production has on another and highlight understandings of access within the context of the greater production system. While most actors engage in activities and trading relations that serve access to markets, non-actors enable these actions, but for different benefits, such as strengthened authority. Lastly, I link aspects of materiality to access, demonstrating how the biogeophysical features of rattan shape actors’ ability to benefit from natural resource products and how markets shape material features of rattan. These findings are significant to the greater bodies of knowledge around the power dynamics of production networks and show the specific mechanisms by which elites capture benefits of rattan. They demonstrate the importance of appreciating the complexity of production networks, which in this case was ill-considered by policy makers and even industry elites themselves

Algorithms for Graph Connectivity and Cut Problems - Connectivity Augmentation, All-Pairs Minimum Cut, and Cut-Based Clustering

We address a collection of related connectivity and cut problems in simple graphs that reach from the augmentation of planar graphs to be k-regular and c-connected to new data structures representing minimum separating cuts and algorithms that smoothly maintain Gomory-Hu trees in evolving graphs, and finally to an analysis of the cut-based clustering approach of Flake et al. and its adaption to dynamic scenarios