Calibration Infrastructure for the GLAST LAT

A system is being built to accommodate a wide range of time-varying data types, including at a minimum hardware status bits, conversion constants, and alignment for the LAT instrument and its prototypes. The system will support persistent XML and ROOT data to begin with; other physical formats will be added if necessary. In addition to the "bulk data", each data set will have associated with it a row in a rdbms database containing metadata, such as timestamps, data format, pointer to the location of the bulk data, etc., which will be used to identify and locate the appropriate data set for a particular application.

GLAST uses the Gaudi framework for event processing. The Calibration Infrastructure includes conversion services, converters and data objects implementing the prescribed Gaudi interfaces (IDetDataSvc, IValidity, ..) so that calibration data will always be valid and appropriate for the event being processed. The persistent representation of a calibration dataset as two physical pieces in different formats complicates the conversion process somewhat: two cooperating conversion services are involved in the conversion of any single dataset.