**3.2 Experiments' specific developments**

All the LHC experiments created their own specific Computing models summarized in the individual Computing Technical Design Reports (TDRs). They do not rely only on the WLCG-provided middleware packages but are also developing some specific components tailored to better comply with their Computing models.

For example, the ALICE experiment has developed a grid middleware suite AliEn (AliCE Environment [30]), which provides a single interface for a transparent access to computing resources for the ALICE community. AliEn consists of a collection of components and services which will be described in the next section. AliEn, together with selected packages of the WLCG-provided middleware, gives a complete framework to the ALICE community to manage and process the data produced by the LHC according to the ALICE Computing model.

All the LHC experiments invested a considerable effort into shielding the users from the underlying complexity of the Grid machinery, trying to provide relatively simple entry points into the Grid. This effort has payed off and is reflected in a considerable number of physicists actually using the WLCG for their analysis.
