[stefek99]

SOP = standard operating procedure.

I would be surprised if it was otherwise.

[tecleandor]

Coming from the DICOM world, for me it's always Service-Object Pair

[DaSHacka]

From the locksmithing world, I thought of System Of Progression at first

Before, of course, realizing no way someone on HN would be talking about obscure locksmith masterkey terminology