Detector Description Framework in LHCb Sbastien Ponce CERN

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Detector DescriptionFramework in LHCbSébastien
PonceCERN
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Topics

• Detector data overview
• Structure, Transient Store, XML backend
• Possible extensions
• Parameters, Full extension
• Condition Database
• Purpose, Implementation, Impact on user
• Tools
• Simulation, Geometry Checker, Visualization

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Data Diagram
Points to
Lvolume
Solid
Material
Resolved on demand
Inherits from

Pvolume
Geometry Info
DetElem
Geometry
Material
Condition
Structure
Conditions
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Transient Store
Detector Data Service
Persistency Service
Ask for Object
Check presence
Ask creation
Load
Algorithm
Lvolume
Cnv
Lvolume
Lvolume
DetElem
Transient Store
Retrieve pointer

• Tree-like structure
• Items identified by a logical name
• Load/update on demand
• Automatic update when new event

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XML Backend

• Easy to read and to parse
• Extensible
• Easy to convert
• Many tools
• Extended using references

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User Extensions
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User Extensions

• Why ?
• In order to implement specific behaviour(e.g.
  answering specific simulation questions)
• Add specific information to elements / conditions
• How ?
• By specializing the Detector Element / Condition
• 3 main possibilities
• Usage of parameters in the XML code
• Specialization of the C object only
• Full extension, including XML, DTD and C
  converters

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Parameter Extension

• Definition of parameters (name, type and value)
  in the XML code
• Vectors of parameters also allowed
• Direct and easy access in C

SmartDataPtrltIDetectorElementgt station
(detSvc(), "/dd/Structure/LHCb/Muon/MStation01")
stdcout ltlt station-gtparam("Al_thickness")
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C Class Extension

• New C class inheriting from DetectorElement
• Any member or method may be added
• Its initialize method is called by the framework.
• A dummy converter is needed (2 lines)

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Full Extension

• Extension of the DTD to define new XML elements
  inside the ltspecificgt element
• Parsing of the new XML code using dedicated
  converters
• Still specialized C objects

ltdetelem name"Head"gt ltspecificgt ltchannelSet
name"Controls"gt ltchannels namein
nb"20"/gt ltchannels nameout
nb"150"/gt lt/channelSetgt lt/specificgt lt/detelemgt
if ("channels" elementName) string name
childElement.getAttribute ("name") int nb
xmlSvc()-gteval(childElement.getAttribute("nb"))
currentChannelSet-gtaddChannel(name, nb)
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Condition Database
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CondDB Purpose

• To deal with time varying data like calibration,
  alignment, environment (temperatures) ...
• Handle several versions of a given data
• Also deal with the geometry, which is also time
  dependent (longer period though)

Version
Time
Data Item
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CondDB Implementation

• Additional service of the framework
• Independent of the type of data contained (XML)
• Based on an abstract interface with several
  possible backends (Objectivity, ORACLE, MySQL)

Detector Data Service
Persistency Service
Condition Service
Ask for Object
Check presence
Ask creation
Ask for data
Retrieve them from Database
Algorithm
DetElem
Abstract interface
DetElem
Cnv
DetElem
DetElem
Transient Store
Retrieve pointer
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Impact on End User

• No impact on the "raw" XML code
• Only references are changed by the usage of the
  "conddb" protocol
• No change at all in the C code the correct
  data are loaded depending on the event time

ltDDDBgt ltcatalog name"Hcal"gt lt!-- Hcal slow
control catalog --gt ltconditionref
href"conddb/CONDDB/SlowControl/Hcal/scHcalscHca
l"/gt lt/cataloggt lt/DDDBgt
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Tools
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XmlEditor Tool

• Specialized XML Editor for Detector data
• Understanding cross file references
• Hides the complexity of XML from the end user
• Tree like structure a la explorer
• Easy drag drop, cut paste
• Insure that the XML is well-formed and valid
• Still writes human readable, indented XML

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XmlEditor Tool
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Geometry Checkers

• Visual checker
• based on David Dawn's Visual Intersection
  Debugger
• Uses GiGa Gaudi interface to Geant4
  applications
• Gaudi Transport Service
• More precise
• More reliable

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Visualization Tool

• Event and geometry viewer
• Interfaced with Gaudi via scripting services

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Visualization (2)
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Conclusion

• A fully functional and stable solution
• Many tools provided
• For XML generation
• For geometry checking
• For visualization
• Used successfully for simulation, reconstruction
  and analysis