摘要
This paper outlines the desgn and prototyping of the ATLAS High Level Trigger(HLT)wihch is a combined effort of the Data Collection HLT and PESA(Physics and Event Selection Architecture)subgroups within the ATLAS TDAQ collaboration.Two important issues,alresdy outlined in the ATLAS HLT,DAQ and DCS Technical Proposal [1] will be highlighted:the treatment of the LVL2 Trigger and Event Filter as aspects of a general HLT with a view to easier migration of algorthms between the two levels;unification of the selective data collection for LVL2 and Event Building.