An Overview of the Deco System: Data Model and Query Language; Query Processing and Optimization

Abstract

Deco is a comprehensive system for answering declarative queries posed over stored relational data together with data obtained on-demand from the crowd. In this overview paper, we describe Deco's data model, query language, and system prototype, summarizing material from earlier papers. Deco's data model was designed to be general, flexible, and principled. Deco's query language extends SQL with simple constructs necessary for crowdsourcing, and has a precise semantics for arbitrary queries. Deco's query execution engine and cost-based query optimizer incorporate many novel techniques to address the limitations of traditional query processing techniques in the crowdsourcing setting. Query processing is guided by the objective of minimizing monetary cost and reducing latency.