Twenty years of diffraction at the Tevatron

Results on diffractive particle interactions from the Fermilab Tevatron p-bar p collider are placed in perspective through a QCD inspired phenomenological approach, which exploits scaling and factorization properties observed in data. The results discussed are those obtained by the CDF Collaboration from a comprehensive set of single, double, and multi-gap soft and hard diffraction processes studied during the twenty year period since 1985, when the CDF diffractive program was proposed. The results obtained on soft and hard diffraction exhibit regularities that point to the QCD nature of the Pomeron. The most striking feature of the data is the s-independence of the single diffractive dσ/dM2 differential cross-section. This scaling behaviour provides a clue to understanding the Pomeron as a composite structure built up from a combination of gluons and/or quarks with the quantum numbers of the vacuum in accordance with QCD color constraints