  In a data warehousing process, the data preparation phase is crucial.
Mastering this phase allows substantial gains in terms of time and performance
when performing a multidimensional analysis or using data mining algorithms.
Furthermore, a data warehouse can require external data. The web is a prevalent
data source in this context, but the data broadcasted on this medium are very
heterogeneous. We propose in this paper a UML conceptual model for a complex
object representing a superclass of any useful data source (databases, plain
texts, HTML and XML documents, images, sounds, video clips...). The translation
into a logical model is achieved with XML, which helps integrating all these
diverse, heterogeneous data into a unified format, and whose schema definition
provides first-rate metadata in our data warehousing context. Moreover, we
benefit from XML's flexibility, extensibility and from the richness of the
semi-structured data model, but we are still able to later map XML documents
into a database if more structuring is needed.
