For the rst time since the emergence of the Web, structured data is playing a key role in search engines and is therefore being collected via a concerted e ort. Much of this data is being extracted from the Web, which contains vast quantities of structured data on a variety of domains, such as hobbies, products and reference data. Moreover, the Web provides a platform that encourages publishing more data sets from governments and other public organizations. The Web also supports new data management opportunities, such as e ective crisis response, data journalism and crowd-sourcing data sets.