Two main ideas (and packages) are worth noting :
Although we do not provide here a dedicated page for the history and concepts of XAS, we refer to pre-existing information in the user manual, in the programmer manual and in the XAS home page. In particular there is an historical account. We provide however a conceptual summary with references.
The activities for the XMM LSS Survey (incorporating also the guaranteed time XMDS survey) are described below together with VIRMOS.