Data Quality Challenges in Community Systems AnHai Doan (University of Wisconsin) Over the past three years, in Cimple, a joint effort between Wisconsin and Yahoo! Research, we have been trying to build community systems. Such systems employ automatic data management techniques, such as information extraction and integration, as well as user-centric Web 2.0-style technologies, to build structured data portals for online communities. As the work progresses, we have encountered a broad range of fascinating data cleaning challenges. Some of these (e.g., data quality evaluation, record reconciliation) also arise in traditional ETL processes. But here they become exacerbated, take on new nuances, or are amenable to novel solutions that exploit community characteristics. Many other challenges however are new, and arise due to the fact that community systems engage a multitude of users of varying skills and knowledge. Examples include how to entice users to collaboratively clean data, how to handle "noisy" users, and how to make certain cleaning tasks easy for "the masses". We describe the challenges and our initial solutions. We also describe the infrastructure support (code, data, etc.) that we can provide, in the hope that other researchers will join and help us address these problems.