Say for example I publish adobe reader, and I have a detection rule for checking if the file C:\Program Files (x86)\Adobe\Acrobat Reader DC\Reader\AcroRd32.exe exist--->If you go with this setting, if the file exist, the application detection rule is passed hence no need to install the application.
It it not recommended to go with simple file detection rule as such like this. Either go with product ID or file version (greater than or equal to) or something that could help you to install latest version.
It all depends on how you identify/tell you have new application to be installed on the devices. is that by product ID or file version etc.
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