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C236

Mapping Auxiliary Persistent Data to C++ Objects in the CDF Reconstruction Framework
Dennis Box1, Paolo Calafiura2, Jack Cranshaw3, Robert Harris1, James Kowalkowski1, Mark Lancaster2, Marjorie Shapiro4
  1. Fermilab
  2. Lawrence Berkeley National Laboratory
  3. Texas Tech University
  4. Univ. of California

Presented by: James Kowalkowski

  Within the CDF event processing software, there is a need for information that is not directly stored with the event, such as calibration and alignment constants. This information is currently stored in relational databases and flat files and is presented to the event processing algorithms as objects. The objects are retrieved using a compound key that can be stored with the event data. The objects and keys are designed to be the algorithm's view of the information in the database. The persistent form will be typically quite different - spanning several relational database tables or retrieved from several files. A database interface management layer exists for the purpose of managing the mapping of persistent data to transient objects that can used by the event processing algorithms. This layer sits between the algorithm code and the code that reads the data directly from permanent storage. At the persistent storage end, it allows multiple back-end mapping objects to be plugged in and identified as data sources at run time by a simple character string. At the user end, it places a get/put interface on top of a transient class for retrieval or storage of objects of this class using a key. The layer allows the user, anywhere in algorithm code, to make requests for specific objects. The persistent storage object creates the object requested by the user from information in the database using the key. In addition to the transient/persistent mapping discussed above, the layer caches objects by key to prevent multiple database accesses from different algorithms for the same objects. The layer also provides a default key mechanism that allows different objects that share the same key type to be managed as a group or set, with a single set identifier. This grouping facility allows entire calibration sets to managed in one place within the reconstruction program and can be used to insure that algorithms retrieve the correct calibration constants for the event being processed.

Short Paper:  Adobe Acrobat pdf 
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