Conditions Database Access Example

                    David R. Quarrie
                    DRQuarrie@LBL.Gov

                      17 Sept 1996


This example uses a hypothetical Sys detector having multiple crystals
with gain and alignment information. The crystals are identified by a 
2-D tag (theta,phi). Digi objects corresponding to this detector are 
contained within the event, themselves being identified by the same 2-D 
tag.

The following classes are defined:

SysDigi         Digi classes for the Sys detector. Accessed via 
                the AbsEvent object.

SysXtalALign    Contains alignment information for each crystal.

SysXtalGain     Contains gain information for each crystal.

SysXtal         Contains all conditions information (geometry,
                alignment, gains, etc.) for each crystal.

SysAllXtalAligns Contains the alignment for all crystals as a HepVector 
                (kept in conditions database) 

SysAllXtalGains Contains the gains for all crystals as a HepVector 
                (kept in conditions database) 

SysXtalMap      Contains mapping between the 2-D space and the
                linear index into the HepVector.

AbsEnv          This is a simple AbsEnv class that illustrates 
                access to conditions database information, as
                well as the ability to add transient objects to it.

The example illustrates how the Digi objects may access their corresponding
Xtal object and thence the gain, alignment and other information. It also
illustrates how some local caching may be performed.


Notes:

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    = This example is not yet functional =
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