This paper deals with the issue of abstracting a data source characterized by one among several possible representation formats. First we show that data source abstraction plays a central role in several important application problems in the area of information system design. Then we propose a new approach which is capable of semi-automatically carrying out the abstraction of a data source possibly encoded according to one among a variety of formats such as structured databases, OEM graphs and XML documents. The capability to handle heterogeneous formats is obtained via the usage of a particular conceptual model, called SDR-Network, which is able to uniformly represent and handle data sources with different formats. As a significant application of the presented data source abstraction algorithm, the construction of an Intensional Repository is also illustrated.