Why are you trying to add dielectrics? I've never heard of them being represented in the GDS, and the parasitic rules from the foundry already include their effects -- that is part of the modeling with xCalibrate that is done to produce the parasitic rules.
Each technology process from the foundry has its own PDK, and assuming the PDK supports Calibre xRC/xACT/xL the PDK includes foundry-certified rules for the parasitics that correctly calculate the effects of their particular manufacturing process. You really don't want to mess with those (which is why they are generally encrypted).
To see more about dielectrics, you could look at the xCalibrate manual, but chances are unless you are a foundry or a university developing a new manufacturing process it won't be much help. You might also check SupportNet -- there are some technotes about handling particular manufacturing structures such as airgaps (again, via xCalibrate -- the foundries already include this stuff in their PDK if they support it).
Thank you for the answer.
Let me explain more of the problem I face.
I recently migrated a layout to a more advanced technology node.
The previous layout has no problem running Calibre PEX with xAct 3D option.
When I ran PEX on the migrated layout, it showed a fatal error "dielectric layers not defined."
So I traced both foundry rule files (in my case not encrypted) and found the difference is the new one misses the lines that define dielectrics in the pex profile.
Those should look something like "metaln_dieln PLANAR xx yy zz."
I thought there is a simple solution to resolve it since all the information I need is in the comments (z coordinates, dielectric coefficients), which includes all info for different profiles.
I suppose those are also generated by xCalibre.
Now my suspicion is as you mentioned, this can only be done by xCalibre, but I don't have the necessary files to regenerate the rule file.
This is frustrating since the missing lines seem to be easy to insert back in.
I haven't used PEX myself in several years, but I checked with someone who is current -- she confirmed that editing the foundry's rules yourself is still strongly discouraged (even PEX Profile) and you should contact the foundry (or MGC Customer Support) to get a working version.