TITLE: Data Software: Design for Change ABSTRACT: Over the past few decades I've worked on a number of software projects that process data. I've never been very good at predicting how the software I develop will be used or how it will evolve. As a consequence I've learned to prepare for the unexpected. Software can be designed from the outset to facilitate change. I'll present a number of policies to support this and illustrate them with examples from Lucene, Hadoop, Avro and other projects.