A data extract is a compressed snapshot of data from a regular data source. This data is contained in a local file and can be updated from the original data source at any time. You have an option to work with an external SQL data source or you can use the Extract Data Source as an intermediate layer.
The DevExpress Dashboard uses database servers that can be configured to use case-sensitive table/column names. For this reason, a database scheme used in dashboards is case-sensitive to prevent any problem when the product is used with such servers.