platform by linking datasets from providers such as European Bioinformatics Institute, Royal Society of Chemistry, UniProt, WikiPathways and DrugBank. This corresponds to the problem of answering queries using views ( aquv ). The legality of this mapping depends on the nature of the correspondence between Gdisplaystyle G and Sdisplaystyle. Such mappings can be specified in 2 ways : as a mapping from entities in the mediated schema to entities in the original sources (the " Global As View " (GAV) approach or as a mapping from entities in the original sources to the mediated schema.

10 ) These approaches combine unstructured or varied data into one location, but do not necessarily require an (often complex) master relational schema to structure and define all data in the Hub. Data integration appears with increasing frequency as the volume (that is, big data 2 ) and the need to share existing data explodes. The virtual database interfaces with the source databases via wrapper code if required. Issues with combining heterogeneous data sources, often referred to as information silos, under a single query interface have existed for some time. Therefore, oreos or Fig Newtons LAV systems must often deal with incomplete answers. In this case Mdisplaystyle M associates to each element of Gdisplaystyle G a query over Sdisplaystyle.