There is no doubt that sdf file contain a large amount of data, but it's all for tools, not preparing for your reading. Certainly, you can read the cell delay information that you concerned, or have a comparation. So, I think it's not for reading.
SDF file has its own standard format, and the syntax is simple. Sometimes it is needed to read this file, plase refer to SDF Standard, you can download it from www.ovi.com
About how to use infomation inside SDF(standard delay format)
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Please refer to the following link:
-- https://www.nandigits.com/sdf_timing.htm
An example about using SDF file with the design.
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GOF, Gates On the Fly
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GOF doesn't load the SDF file directly, instead it creates an SDF index file first.