Report of the Event Tag Review and Recommendation Group

In order to facilitate access to the large volumes of data (multiple petabytes per year) which will be produced during data taking and Monte Carlo production at ATLAS, work has proceeded on building a system of event-level metadata to allow selections of a subset of events to use as input to an analysis. This was included in the ATLAS Computing Model and was first studied and implemented by the Physics Analysis Tools group based on the decisions of the ESD/AOD Task Force. They used tools developed and supported by the CERN IT group and the ATLAS Database group. During 2005 this structure was put through various tests and evaluations. Also, work by physicists on reconstruction and analysis led to an improved understanding of the requirements on the TAG. This report addresses the effect of these new inputs on the previous work with regard to content and the infrastructure needed to support it.