Problem 2506

Summary: Missing physics datasets require users to be clairvoyant
Product: Geant4 Reporter: Tom Roberts <tjrob>
Component: global/managementAssignee: Ben Morgan <Ben.Morgan>
Status: ASSIGNED ---    
Severity: enhancement    
Priority: P4    
Version: 11.0   
Hardware: All   
OS: All   

Description Tom Roberts 2022-08-17 18:03:42 CEST 
Every dataset has THREE different names: 1) its name, 2) the environment variable name, 3) the file name. The file name is just its name with ".tar.gz" appended, but there is little rhyme or reason relating the name to the environment variable.

Error messages give the environment variable. The download page gives the dataset names. So users must be clairvoyant to figure out which dataset needs to be downloaded, installed, and set into the environment.

From this error message:
**************************************************************************
*** G4Exception: had0707
***    severity: Fatal Exception
***   issued by: G4LevelReader()
*** description: Environment variable G4LEVELGAMMADATA is not defined
**************************************************************************

How does a user know to download G4PhotonEvaporation.5.7.tar.gz????

Every dataset has this problem, though some are more obvious than others.

(Yes, the Installation Guide has a table mapping dataset names to environment names. Users must be very experienced or clairvoyant to know to look there.)

(Yes, dataset names include version numbers and environment variables cannot. But if this environment variable was "G4PhotonEvaporation" it would be A LOT more obvious how to fix the problem.)

Bottom line: each object should have a SINGLE name that is used throughout.
Comment 1 Tom Roberts 2022-08-17 18:06:17 CEST 
Potential workaround: Put the environment variable name into the description of each dataset in the download page.

This does not really solve the problem, but at least reduces the burden on users.
Comment 2 Ben Morgan 2022-12-09 18:27:40 CET 
As of the latest release 11.1, the configuration of the datasets has been rationalized as documented here: https://geant4-userdoc.web.cern.ch/UsersGuides/InstallationGuide/html/postinstall.html#environment-variables-for-datasets

That doesn't solve the direct enhancement request here, but is hopefully a start. Additional documentation and clarifying/unifying the tarball and envvar names need a little thought to ensure backward compatibility for downstream build/packaging scripts.