Efficient and accurate systems for querying unstructured data

Abstract: (shortened) In recent years, automatic analysis over this unstructured data has become possible via machine learning (ML). Analysts can use ML to extract structured information from these unstructured sources, such as object types and location from a video. The structured information can subsequently be used in downstream analysis, e.g., the urban planner can count the number of cars that passed by an intersection. Unfortunately, using ML for these analyses is challenging. Deploying ML is prohibitively expensive for many organizations: naively analyzing a year of video from a small town can cost millions in cloud compute credits. ML methods are also unreliable, returning incorrect results, which can lead to downstream errors. Finally, deploying ML for analytics requires knowledge of deep learning, data systems, programming, and other technical skills. In light of these challenges, we make two observations: many applications can tolerate approximations, if there are guarantees on accuracy, and methods for answering unstructured data queries range by up to 10 orders of magnitude in cost. In this dissertation, we develop systems and algorithms for efficient and reliable unstructured data analytics, leveraging the two observations. Instead of returning exact answers, we return approximate answers generated by cheap approximations to expensive ML methods. Our systems can return statistically valid answers on a wide range of query types, including selection, aggregation, and limit queries. Furthermore, our systems can be up to orders of magnitude cheaper than standard methods of answering queries Comments