the problem of answering queries using views (AQUV). In GAV systems, a system designer writes mediator code to define the query-rewriting. Each element in the user's query corresponds to a substitution rule just as each element in the global schema corresponds to a query over the source. Query processing simply expands the subgoals of the user's query according to the rule specified in the mediator and thus the resulting query is likely to be equivalent. While the designer does the majority of the work beforehand, some GAV systems such as Tsimmis involve simplifying the mediator description process. In LAV systems, queries undergo a more radical process of rewriting because no mediator exists to align the user's query with a simple expansion strategy. The integration system must execute a search over the space of possible queries in order to find the best rewrite. The resulting rewrite may not be an equivalent query but maximally contained, and the resulting tuples may be incomplete. the GQR algorithm is the leading query rewriting algorithm for LAV data integration systems. In general, the complexity of query rewriting is NP-complete. If the space of rewrites is relatively small, this does not pose a problem — even for integration systems with hundreds of sources. Medicine and Life Sciences Large-scale questions in science, such as real world evidence, global warming, invasive species spread, and resource depletion, are increasingly requiring the collection of disparate data sets for meta-analysis. This type of data integration is especially challenging for ecological and environmental data because metadata standards are not agreed upon and there are many different data types produced in these fields. National Science Foundation initiatives such as Datanet are intended to make data integration easier for scientists by providing cyberinfrastructure and setting standards. The five funded Datanet initiatives are DataONE, led by William Michener at the University of New Mexico; The Data Conservancy, led by Sayeed Choudhury of Johns Hopkins University; SEAD: Sustainable Environment through Actionable Data, led by Margaret Hedstrom of the University of Michigan; the DataNet Federation Consortium, led by Reagan Moore of the University of North Carolina; and Terra Populus, led by Steven Ruggles of the University of Minnesota. The Research Data Alliance, has more recently explored creating global data integration frameworks. The OpenPHACTS project, funded through the European Union Innovative Medicines Initiative, built a drug discovery platform by linking datasets from providers such as European Bioinformatics Institute,