A Declarative Framework for Big Graph Analytics and their Provenance

Recent years have witnessed an explosion in size of graph data and complexity of graph analytics in fields such as social and mobile networks, science and advertisement. Analyzing and extracting knowledge from Big Graphs (in analogy to Big Data) is hard. The size of Big Graphs necessitates the use of distributed infrastructures and parallel programming. Moreover, implementing performant and correct analytics requires in depth knowledge of both algorithm and input data. Developers of graph analytics face two major challenges: i) There is a myriad of Big Graph processing frameworks, each uses a different imperative programming language and implements different low-level optimizations. Developers are burdened with understanding the low-level characteristics of an execution framework that suits best their algorithms and data. ii) Assessing the quality of both data and analytics is a tedious and manual task. Devising new graph analytics is an iterative process, where developers incrementally refine their algorithms and clean their data by analyzing results, correcting for errors and run again until the end results are satisfiable. In this dissertation we offer a declarative framework that addresses the entire life-cycle, from designing to executing, of Big Graph analytics. Our approach uses a single language for both authoring graph analytics and fine-tuning them. Specifically, this dissertation makes the following two main contributions:We design and demonstrate Datalography, the first approach for declarative graph analytics on Vertex-Centric graph processing engines. To accommodate different programming models, we design and implement a compiler that takes general Datalog queries and rewrites them into distribution-aware queries that can be efficiently evaluated on any Vertex-Centric framework. Moreover, our compiler implements automatic and transparent to the user optimizations in the form of logical query rewritings and thus are portable to any Vertex-Centric system. We demonstrate the effectiveness of our approach with an experimental evaluation on real-world graphs that indicates Datalography offers superior performance when compared to native, imperative implementations.Our second contribution is a novel provenance management approach that enables developers to customize provenance capturing and analysis with twofold benefits: the amount of captured provenance is minimized to include only the necessary information and analysis is extended beyond the traditional tracing queries. We present formal semantics of our provenance query language, based on Datalog, and identify an important class of queries that can be evaluated online, simultaneously with the graph analytic. We showcase our approach with Ariadne, a provenance management system that supports efficient debugging, auditing and fine-tuning of graph analytics