Such service type contains built-in integration mechanisms with the SaaS-products, cloud apps, bases and some kind of on-premises tools like Microsoft Excel. As distinct from the solutions for real data virtualization with multi-level representing and delegated query execution, these services open access to standartized API, facilitating data exchange with cloud sources in medium-scale projects. However, their capabilities are insufficient for project realization related to big data analysis, critically important enterprise systems, mainframes, large data bases, unstructured files and data.