Complexity Postdoctoral Fellowship


My goal is to integrate themes from my previous work on peer learning, computational creativity, and social machines in an agent-based model of a popular question-and-answer website, Stack Overflow. This will realise Turing’s vision of artificial agents that are “able to converse with each other to sharpen their wits,” and could potentially open the way to superhuman AI for computer programming.

Stack Overflow is the flagship site on the open source Q&A network, Stack Exchange. It contains over 18 million user-contributed questions on computing topics. About 13 million of these questions have vetted answers, marked with votes that give an indication of their value. Questions are similarly rated. These signals establish contributors’ reputations, and should be useful for building AI tools based on the corpus. Notwithstanding, a recent generative experiment entitled Stack Roboflow produced only meaningless ersatz questions and answers.Rabbit blowing a trumpet

My proposal unfolds into two overarching objectives. These are reading technical texts into knowledge representations that the computer can reason about, and developing programs that can act on these representations to pose and solve practical problems. A key innovative aspect of the proposal is that an evolving population of rule-based agents will be employed to assist with both tasks. Agents will gain points for asking and answering questions about Stack Overflow content.

Recent developments in natural language processing make the knowledge extraction task plausible. Powerful tools are now available off-the-shelf, including pretrained language models that can be fine tuned around specific tasks. Question-answering systems based on Google’s BERT perform at a superhuman level on a standard reading comprehension task. In the programming domain, there have been advances in extraction from code into higher-level abstract representations of process. Argument modelling has been applied by myself and coauthors to sample Q&A dialogues and other technical texts. The combined constraints of the Q&A format and the technical focus make models of semantic structure more straightforward than for domain-nonspecific free text. Given sufficient structural clues, machine learning techniques can be applied to technical texts to categorise their statements. These are key landmarks on the way to the first objective.

The real test of meaningfulness will come in the use of the extracted information, via evaluation of agent performance on both synthetic tasks and human-in-the-loop applications. At the level of anatomy, I am interested in exploiting the similarity between networks of related questions and answers and the Tangled Program Graphs (TPG) approach, in which teams of programs are assembled and networked together, and a team’s fitness is scored jointly. TPG has performed comparably with agents built using deep learning on video game challenges, but TPG agents are trained on standard CPU hardware. At the level of individual learning and behaviour, I plan to draw upon the active inference paradigm from cognitive science, in which agents actively seek to maximise the evidence for their sensory model and minimise uncertainty. Designs based on active inference have been realised in neural network-based agents, and demonstrated in concept learning and reinforcement learning tasks. At the level of collective behaviour, Elinor Ostrom’s institutional analysis and development (IAD) framework will be used to guide and constrain agent interactions, beginning with a model of the institutions currently in place on Stack Exchange. IAD is based on rules, norms, and strategies, for example, regulatory rules describe “ATTRIBUTES of participants who are OBLIGED, FORBIDDEN, OR PERMITTED to ACT (or AFFECT an outcome) under specified CONDITIONS, OR ELSE.” To scaffold evaluation, metrics that have previously been used to measure learning on Stack Exchange can be adapted. Crowdsourced reading comprehension questions and simple exercises derived from existing Q&A would provide a further route to evaluation. Agents will also generate their own questions early on in the project, which is expected to boost their question-answering ability. Computational questions typically have another source of ground truth, namely computational tests, and agents will accordingly be given access to sandboxed computing environments. Performance will be connected back to choices made in content extraction, and both will improve together.

To situate this proposal relative to other work in formalisation, one notes that the contents of a Q&A site have a structural resemblance to Kolmogorov’s calculus of problems. Whereas in formal mathematics we would write x y for a valid inference, now in a certain sense we have Q A. The essence of Stack Exchange is that obtaining a useful answer typically reduces to asking a suitable question. It has also been observed that a well-posed question can fully constrain the form taken by the answer. However, most questions on Stack Exchange are not so formal. Just as questions must be set in an appropriate context, answers often include contextually appropriate exposition. Far from being comprised of atomic actions, answers often refer to preexisting Q&A, use them as informal rules, and describe the mutual accommodation of their contents. Agents in the sense outlined above will be playable collections of interlinked rules, somewhat akin, as it happens, to HyperCard’s stacks.

Although Stack Overflow is ‘gamified’ through the reputation mechanism, in comparison to most game playing research, the programming domain is more open. Professional programming practice relies on accumulated design patterns and various ergonomic conveniences, and it has at least as much to do with humans as it does with computers. In order for agents to explore this domain, they will need stepping stones, starting from the simplest possible tasks and growing in complexity. This principle is illustrated in a 2004 SFI working paper by W. Brian Arthur and Wolfgang Polak. In the programming domain, we can begin to develop agents’ abilities using simplified exercises, often referred to as koans. Similarly, simple process models and argument structures will be introduced to scaffold content creation. As the work progresses, agents should be able to identify at first simple and then increasingly complex patterns and regularities, and use these to encode new behaviours.

I have allocated time to learn new things in focused bootcamps (involving participation in organ ised summer schools or research visits where these can be arranged), to integrate ideas from SFI collaborators about both design and theory, and to involve external collaborators. My plan is to hold an agent programming competition in month 18 of the project, once the basic infrastructure is in place. This friendly competition will help to place AI for programming solidly on an open science footing. In recognition of the fact that human Q&A do not exist in a vacuum, in month 20 of the project, I propose to integrate the system with Github’s API, so that agents can ask and answer questions about ongoing software development. In month 22, I propose a tutoring study, which could potentially take place in situ within the Github issue tracker. I have not laid out a timetable beyond two years. From a project management standpoint, the biggest risk is that some aspects of the proposed work may overrun, and in this regard the third year provides a buffer. On the other hand, if the engineering aspects of the project are highly successful, applications and policy will be foregrounded.

Milestones and deliverables for first 24 months of the project.

M1 Gather data via Stack Exchange APIs M13Institution modelling using IAD
M2 Argumentation-theoretic analysis M14Integrate themes from SFI collaborators
M3Process model analysisM15Develop infrastructure for contributors
M4ML/NLP bootcampM16Agents writing agents
M5Initial ML baseline, e.g., match Q↔AM17Agents writing institutions
M6Hierarchical ML for content extractionM18Organise first contest
M7Active Inference bootcampM19Publication: Artificial Intelligence
M8Agent modelling and sandbox setupM20Integrate with Github API
M9Curate koans and develop solverM21Integrate themes from SFI collaborators
M10Study with crowdsourced exercisesM22Study in an online tutoring application
M11Study with agent-written questionsM23Publication: Science
M12Publication: IJCAIM24Time off and plan Year 3

This proposal is inspired in part by a project led by Tom Hales at the University of Pittsburgh which aims to use machine learning to help build a large collection of computationally-meaningful mathematical objects. The research proposed here will provide groundwork for flexible reasoning about such contents when they are available. Of course, Q&A can be addressed to any topic. In a 2017 essay, Arthur describes an emerging virtual, autonomous economy, in which the “intelligence is selforganizing, conversational, ever-adjusting, and dynamic.” Stack Exchange has these properties, and importantly, its primary application is to support meaningful work by its users. Using it as a model for AI means that we take as a starting point a system for which economic access and pro-social engagement are very much in scope. These are values to be conserved and enhanced. Against any utopian or dystopian readings, Turing’s assessment that intelligent machines will eventually take control is considerably ameliorated by Ostrom, insofar as control will be distributed across an array of institutions. The research project will make technical contributions to the domains of question-answering and AI for programming. At its heart, it is an investigation of what it means to be part of a culture of shared inquiry.

Statement of interest in SFI

Stack Exchange represents a portion of what could be called the human “noöme”, a noetic heritage that is as necessary for our collective survival as the micro-biome is to individual persons. It exhibits a rich set of dynamics in language, learning, and knowledge economy. Moving from human apprehension of these dynamics towards machine understanding will profitably draw on resources and insights from across SFI, drawing as well on its rich history. In particular, an Artificial Stack Exchange can be seen as a sequel to the classic Artificial Stock Market. The current proposal shares “a desire to understand the impact of agent interactions and group learning dynamics.” I believe I already share some of SFI’s cultural DNA.

Career Highlights

My pursuit of a mathematics education and subsequent doctorate in Knowledge Media were inspired by an edited volume in ecological anthropology, The Question of the Commons, which included papers that used mathematical methods to study culture. I became interested in mathematics as culture, and in the knowledge commons. With an eye on Deep Blue, I saw computers as an essential part of the landscape. My student research related to D’Arcy Thompson-style “Growth and Form” in simple geometrical systems has guided my subsequent thinking about the structure of knowledge and learning dynamics. Recent work bridges between mathematics, philosophy, argumentation theory, and computing, and has resulted in high-quality journal publications.

Figure 1: Meta-CAs with 256 states, subject to a Baldwin effect, tinted to show the evolution of Rule 110 and related variants (deterministic and low-mutation-rate versions) Meta-CAs with 256 states, subject to a Baldwin effect

I have attached a 2015 workshop paper on cellular automata that illustrates my interest in themes studied at SFI. The paper integrates ideas from cognitive science and social theory. I should point out that the question raised by this paper is by no means solved; I did make some further progress after the publication, see Figure 1. The unsolved issues from this paper could serve as a conversation stater with SFI researchers. It offers an analogy for the work I am proposing. Below, I outline some potential connections with themes that people working at or affiliated with SFI, and the ways in which these collaborations could support the foregoing proposal.

I mentioned W. Brian Arthur’s The Nature of Technology as a theoretical framework that can be reused here. Helena Miton’s work on “the role of institutions in generating and transmitting technical knowledge and practices” would find concrete analogues within the work I have proposed. Albert Kao’s research on “how learning as part of a collective results in behavior that is fundamentally different from that learned in isolation” is related to interests that run through my PhD thesis, my subsequent work in the Peeragogy project, and that continues to be important for this proposal. Jessica Flack’s research on “collective computation” and “extracting strategies… from time-series data and constructing stochastic strategic circuits” could help with modelling and improving learning outcomes within the system I have proposed. In Chapter 6 of my PhD thesis, I used a statistical method to model human learning, but this could go further. Tyler Marghetis studies “high-level, abstract thinking,” and there is some overlap with his research and my earlier work in concept blending. One of the interesting challenges in the proposal is the lack of an overt embodiment for the agents I have proposed. David Krakauer’s classic work on language evolution and interest in “complex feed-backs present between individuals and their environments” will be relevant to my proposal, as I seek to understand technical language and practices. David Kinney’s work on “a pragmatic measure of explanatory depth” will be relevant to shaping questions and answers, as well as agent protocols. Jürgen Jost aims to “investigate the basic principles of structural knowledge”, which is close the interests I have described.

I should acknowledge that neither my education nor my career has been particularly traditional. SFI is home to others who have sought out high-risk, high-reward learning opportunities. My skills, knowledge, and experience would complement those of SFI’s current cohort. The culture of shared inquiry would be an ideal incubator for the next steps in my work.