The Declarative Imperative Experiences and Conjectures in Distributed Logic Joseph M. Hellerstein University of California, Berkeley
[email protected] ABSTRACT The juxtaposition of these trends presents stark alternatives. The rise of multicore processors and cloud computing is putting Will the forecasts of doom and gloom materialize in a storm enormous pressure on the software community to find solu- that drowns out progress in computing? Or is this the long- tions to the difficulty of parallel and distributed programming. delayed catharsis that will wash away today’s thicket of im- At the same time, there is more—and more varied—interest in perative languages, preparing the ground for a more fertile data-centric programming languages than at any time in com- declarative future? And what role might the database com- puting history, in part because these languages parallelize nat- munity play in shaping this future, having sowed the seeds of urally. This juxtaposition raises the possibility that the theory Datalog over the last quarter century? of declarative database query languages can provide a foun- Before addressing these issues directly, a few more words dation for the next generation of parallel and distributed pro- about both crisis and opportunity are in order. gramming languages. 1.1 Urgency: Parallelism In this paper I reflect on my group’s experience over seven years using Datalog extensions to build networking protocols I would be panicked if I were in industry. and distributed systems. Based on that experience, I present — John Hennessy, President, Stanford University [35] a number of theoretical conjectures that may both interest the database community, and clarify important practical issues in The need for parallelism is visible at micro and macro scales.