Practical Challenges of Learning andRepresentation for Large Graphs


An ever increasing amount of the humanity’s information is being stored in large graphs. The world wide web, digital social networks, e-commerce platforms and chat networks now contain digital traces of the majority of living humans. Many of the most valuable companies ever created are dedicated to organising, managing and extracting useful information from large digital graphs. Machine learning has been shown to be an important tool for automating this task. Discovering scalable machine learning systems, to extract useful information from graphs, is a problem of great practical significance. Interesting graphs, such as the web graph, often contain more information than can be stored on a single computer, and so working with the raw data presents considerable challenges. Graph representations are often employed that encapsulate key properties of the underlying data and enable certain tasks to be performed effciently, at the expense of others. Representations are chosen to balance time complexity, space complexity and predictive performance on a downstream task, such as labelling vertices with attributes. We are concerned with problems of extracting and inferring information from large graphs and applying the results in deployed commercial systems. The research revolves around two large-scale machine learning projects (1) A system for searching and organising data from social media graphs (2) A system to profile customers through their interactions with products on an e-commerce platform. We use representations of graphs to allow algorithms to be run faster, cheaper and more accurately. Doing so allows us to satisfy systems constraints that could not be achieved by operating directly on the raw data. We demonstrate how careful choices of representation can be used to improve machine learning performance on several real-world tasks. We do this under challenging industrial constraints such as real-time serving, runtime costs or maintainability