View - HEPHY

Figure 3.11: Generic state machine for a DAQ or detector component from the viewof the run control system.as alignment parameters, detector geometry or configuration settings. Each Conditionis also associated with an interval of validity (IOV) which describes which events itapplies to.CMSSW provides a Python-based configuration language which allows users to builda processing path out of several types of modules. This configuration defines the selectionand order of modules to run, as well as the values for the modules’ configurationparameters. Figure 3.12 contains a schematic overview of the components involved ina CMSSW process. Modules fall into one of the following categories:• Input modules provide event data from an external source, such as a data file ora network stream.• Producers extend the event data by adding additional records, such as reconstructedtrack data computed from raw detector hits.• Filters are used in a configured path to select a subset of events based on theircontents, for example applying a quality cut in a physics analysis.• Analyzers do not modify the contents of the event, but have read-only access toits data. They can be used to create histograms or reports of the events analyzed.• Output modules store the events after processing.Framework modules use the event content as their only communication interface. Arecord inside an event, also called a product, is identified by its data type and a numberof labels. In addition, the framework stores provenance information that allows a lateruser to determine the modules and configuration involved in its generation.Event Data ProcessingThe initial software view of the detector readout consists of a list of binary streamsread out from the various FED units in the system. Starting with the HLT, later33