  Nowadays, many decision support applications need to exploit data that are
not only numerical or symbolic, but also multimedia, multistructure,
multisource, multimodal, and/or multiversion. We term such data complex data.
Managing and analyzing complex data involves a lot of different issues
regarding their structure, storage and processing, and metadata are a key
element in all these processes. Such problems have been addressed by classical
data warehousing (i.e., applied to "simple" data). However, data warehousing
approaches need to be adapted for complex data. In this paper, we first propose
a precise, though open, definition of complex data. Then we present a general
architecture framework for warehousing complex data. This architecture heavily
relies on metadata and domain-related knowledge, and rests on the XML language,
which helps storing data, metadata and domain-specific knowledge altogether,
and facilitates communication between the various warehousing processes.
