Cloud computing is facilitating unlimited access to the computing and storage resources needed to build applications. The underlying infrastructure manages such resources transparently, without demanding the application manage or reserve more resources than those it really requires. Therefore, database management systems have exploded into cloud services that must be tuned and composed for efficiently and cost-effectively managing, querying, and exploiting huge data sets. In this talk, we will address a querying approach that consists of composing services that provide data and data management functions (aggregation, storage, refreshment). We will discuss how query processing is tuned with respect to the cost of accessing data and services, the cost of using cloud resources for executing the query, and the mashing up of results according to quality dimensions of completeness, data provenance, and data freshness. We will examine how this approach has provided solutions for e-government applications that integrate services from different countries.