If the Current Clique Algorithms are Optimal, so is Valiant's Parser

The CFG recognition problem is: given a context-free grammar $\mathcal{G}$ and a string $w$ of length $n$, decide if $w$ can be obtained from $\mathcal{G}$. This is the most basic parsing question and is a core computer science problem. Valiant's parser from 1975 solves the problem in $O(n^{\omega})$ time, where $\omega<2.373$ is the matrix multiplication exponent. Dozens of parsing algorithms have been proposed over the years, yet Valiant's upper bound remains unbeaten. The best combinatorial algorithms have mildly subcubic $O(n^3/\log^3{n})$ complexity. Lee (JACM'01) provided evidence that fast matrix multiplication is needed for CFG parsing, and that very efficient and practical algorithms might be hard or even impossible to obtain. Lee showed that any algorithm for a more general parsing problem with running time $O(|\mathcal{G}|\cdot n^{3-\varepsilon})$ can be converted into a surprising subcubic algorithm for Boolean Matrix Multiplication. Unfortunately, Lee's hardness result required that the grammar size be $|\mathcal{G}|=\Omega(n^6)$. Nothing was known for the more relevant case of constant size grammars. In this work, we prove that any improvement on Valiant's algorithm, even for constant size grammars, either in terms of runtime or by avoiding the inefficiencies of fast matrix multiplication, would imply a breakthrough algorithm for the $k$-Clique problem: given a graph on $n$ nodes, decide if there are $k$ that form a clique. Besides classifying the complexity of a fundamental problem, our reduction has led us to similar lower bounds for more modern and well-studied cubic time problems for which faster algorithms are highly desirable in practice: RNA Folding, a central problem in computational biology, and Dyck Language Edit Distance, answering an open question of Saha (FOCS'14)

"Kelly is a Warm Person, Joseph is a Role Model": Gender Biases in LLM-Generated Reference Letters

Large Language Models (LLMs) have recently emerged as an effective tool to assist individuals in writing various types of content, including professional documents such as recommendation letters. Though bringing convenience, this application also introduces unprecedented fairness concerns. Model-generated reference letters might be directly used by users in professional scenarios. If underlying biases exist in these model-constructed letters, using them without scrutinization could lead to direct societal harms, such as sabotaging application success rates for female applicants. In light of this pressing issue, it is imminent and necessary to comprehensively study fairness issues and associated harms in this real-world use case. In this paper, we critically examine gender biases in LLM-generated reference letters. Drawing inspiration from social science findings, we design evaluation methods to manifest biases through 2 dimensions: (1) biases in language style and (2) biases in lexical content. We further investigate the extent of bias propagation by analyzing the hallucination bias of models, a term that we define to be bias exacerbation in model-hallucinated contents. Through benchmarking evaluation on 2 popular LLMs- ChatGPT and Alpaca, we reveal significant gender biases in LLM-generated recommendation letters. Our findings not only warn against using LLMs for this application without scrutinization, but also illuminate the importance of thoroughly studying hidden biases and harms in LLM-generated professional documents.Comment: Accepted to EMNLP 2023 Finding

Applicability of HCI Techniques to Systems Interface Design

PhDThis thesis seeks to identify reasons why HCI techniques are unsuitable for application in real world design projects. User-oriented systems design and evaluation require that many considerations such as the psychology of users, the applications and target tasks be born in mind simultaneously. A selection of influential HCI design and evaluative techniques from HCI research literature are reviewed and characterised in terms of their analytic scope. Two studies of systems designers' approaches to user-oriented design and evaluation were carried out in order to gain a clearer picture of the design process as it occurs in applied and commercial projects. It was found that designers frequently lack adequate information about users, carrying Out, at best, informal user-evaluations of prototypes. Most notably HCI design and evaluative techniques, of the type common in the literature, are not being used in applied and commercial design practice. They seem to be complex, often limited in scope, and possessed of inadequate or unrepresentative views of the design process within which they might be applied. It was noted that design practice is highly varied with only a small number of common goal directed classes of activity being identified. These together with observed user-oriented information sources and design constraints provide a useful schema for viewing applied and commercial design practice. A further study of HCI specialists' practice in commercial environments was undertaken, in order to identify particular user-oriented design approaches and HCI techniques suitable for application in practice. The specialists were able to describe desirable, and undesirable properties of the techniques they used which made it possible to identify a list of specific desirable features for HCI techniques. A framework for assessing applicability of HCI techniques was developed from the findings of the thesis. This is demonstrated using an example project from the design studies and may prove valuable in supporting design, evaluation, critiquing and selection of HCI techniques

The Government’s Forward Regulatory Programme

Gives an overview of the Forward Programme, which identifies 308 regulatory changes that may be implemented between April 2010 up to and including April 2011 (comprising 265 new measures and 43 simplifications of existing measures). The Forward Programme is intended to provide greater transparency to the Government’s regulatory intentions as they impact on business

Tutoring systems based on user-interface dialogue specification

This thesis shows how the appropriate specification of a user interface to an application software package can be used as the basis for constructing a tutorial for teaching the use of that interface. An economy can hence be made by sharing the specification between the application development and tutorial development stages. The major part of the user-interface specification which is utilised, the task classification structure, must be transformed from an operational to a pedagogic ordering. Heuristics are proposed to achieve this, although human expertise is required to apply them. The report approach is best suited to domains with hierarchically-ordered command sets. A portable rule-based shell has been developed in Common Lisp which supports the delivery of tutorials for a range of software application package interfaces. The use of both the shell and tutorials for two such interfaces is reported. A computer-based authoring environment provides support for tutorial development. The shell allows the learner of a software interface to interact directly with the application software being learnt while remaining under tutorial control. The learner can always interrupt in order to request a tutorial on any topic, although advice may be offered against this in the light of the tutor's current knowledge of the learner. This advice can always be over-ridden. The key-stroke sequences of the tutorial designer and the learner interacting with the package are parsed against an application model based on the task classification structure. Diagnosis is effected by a differential modelling technique applied to the structures generated by the parsing processes. The approach reported here is suitable for an unsupported software interface learner and is named LIY (`Learn It Yourself'). It provides a promising method for augmenting a software engineering tool-kit with a new technique for producing tutorials for application software