For example, in the following two lines, only the presence of a part no for the last manufacturer distinguishes them. Doesn't that make the second a duplicate of the first with missing information? Ie. redundant?

Grrr. That's what I was trying to avoid when presenting this data. Remember when I said I'd be trimming off a number of the columns? That's what happened.

A lot of the data is redundant - that's just how it's organized - but not because it's for different vehicles or whatever; it's because whoever put it together didn't use an easier way to say "vendor X's plugs 123,124, and 125 match vendor A's plug 999". Instead, they end up saying

A    B    C    D    X
999  001  002  003  123
999  001  002  003  124
999  001  002  003  125
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It's dumb, and I know it's one of the things I have to factor out - but I figured that I'd be taking care of lots of redundancy anyway, and this would just get taken care of as part of the parsing process.

My point is, that whilst plugs from different manufacturers may be interchangable for a given vehicle, each manufacturers plugs have different ranges of operating parameters, which means that plugs from two different manufacturers are not interchangable for all applications.

I assure you that this is not the way it works; plugs with different operating parameters get a different part number. The parameter ranges vary widely, but they're standardized - for exactly the reasons you state - and they're comprehensible as data.

I was at an auto parts store two days ago, and had them look up a plug for me - an NGK B7HS-10 - and they pulled up a screen that showed all the equivalents, which exactly matched the list that I had. They never asked me what vehicle I had, and it wouldn't have helped them if they did: it was a Yamaha 15HP outboard motor, and I no auto parts store is going to list that as a vehicle. :)