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/data/refman/pasoursint/CMSSW_6_1_2_SLHC2/src/FWCore/Utilities/interface/Presence.h

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00001 #ifndef FWCore_Utilities_Presence_h
00002 #define FWCore_Utilities_Presence_h
00003 
00004 // -*- C++ -*-
00005 
00006 /*
00007   An interface class defining a presence.  A presence is an object that an 
00008   executable can instantiate at an early time in order to initialize 
00009   various things.  The destructor
00010   takes action to terminate the artifacts of the run() method.
00011   
00012   The prototypical use of this is to establish the MessageServicePresence.
00013   That class appears in MessageService, which is a plugin.  By using this
00014   abstract class, we can arrange that cmsRun, in Framework, has no link
00015   dependency on MessageService.  Instead, the MessageServicePresence is 
00016   dynamically (run-time) loaded.  
00017 */
00018 
00019 namespace edm {
00020 
00021   class Presence {
00022   public:
00023     Presence() {}
00024     virtual ~Presence() = 0;
00025   };
00026 }
00027 #endif // FWCore_Utilities_Presence_h