[thredds] startTimeSubstitutionPattern

Hello,
    Can someone point me to some detailed documentation on how to use the 
addTimeCoverage element. In particular the starttimeSubstitutionPattern and 
datasetNameMatchPattern. I have files with a julian date that I would like to 
provide time coverage metadata. I have been looking at:

http://www.unidata.ucar.edu/projects/THREDDS/tech/cataloggen/devel/datasetScanElement.html

But that doesn't really describe what happens with the value of 
startTimeSubstitutionPattern


Thanks!!

Jeff