This is the best place I know to get a definitive answer quickly.
which is correct
or is this better
Original is number 1, but it doesn’t feel quite right
#1 is perfectly correct. What feels wrong about it?
#2 is putrid.
#3 is wordy.
data is collective right? #1 is singular,
when you have data it is already a collection…so the “a collection of” is redundant, unless you are specifying that you collected data from different sources and aggregated it?
it just feels hinky…
I also feel datums is pretentious…
Sorry - what makes #3 wordy - I only added one word?
It can be either plural or singular, depending on how it’s used. If you can substitute “information” for it, it’s singular. If you would instead substitute “facts”, it’s plural.
But regardless, the verb “identifies” belongs to “collection”, not “data” or whatever you decide upon.
EDIT: Or does it? We might need more context there.
They all sound wordy. Can you give us a full sentence so we can see how the whole thing reads?
While “data” in common usage is normally a collective noun, don’t forget that it is originally the plural of datum: take each datum you discover/receive and array them together, and you have data. Nothing wrong with #1 – un;ess there’s a reason for specifying a particular collection, calling for the “the” of #3 over the “a” of #1. Precisionist usage thinks that “that” refers back to “collection” and calls for “identifies”; fairly standard usage sees it as referencing “data” and would use “identify.” (Paging twickster to confirm my analysis here.)
Datum is singular and data is plural (or collective). Ain’t no datums.
Thanks for this, my grammar is not so strong as to say exactly why I don’t like it…
Complete sentence in context.
“The methodology behind the TQCS accreditation system employs a collection of constantly upgraded qualitative and quantative data that identifies and benchmarks good corporate practices”
If it were up to me I would remove “a collection of” entirely and be done with it, but not written by me and I don’t want to make such a change.
I think they’re trying to say that they measure many different things at many different sources by the use of “a collection of” so am wary of taking it out, but aren’t many different single measurements more properly referred to in the singular?
While TECHNICALLY “data” is plural, based on Latin, that’s really obsolete. The language evolves, and “data is” is perfectly acceptable usage.
I don’t see anyone arguing that we should still be using “thou” for second person singular.
Agreed - I use “the data is” all of the time.
My problem though is with “a data is” which is what (I think) the sentence in question logically gets simplified to
OK but there still ain’t no “datums are.” 
I think ‘data points’ gets around the problem, even if it is redundant.
You’re all worried about “data” and using “benchmark” as a verb?
“TQCS accreditation uses a set of constantly revised qualitative and quantative data to identify and measure good corporate practices.”
“TQCS accreditation involves finding objective ways to compare the effectiveness of different corporate practices.”
Version 1 says what you want to say with fewer words, but retains some of the corporate jargon and buzzwords you seem to be fond of. I would be inclined to prune ‘to identify and measure’ to just ‘to measure’, given that it’s hard to measure something that you haven’t identified. However, it’s conceivable that they could be regarded as distinct tasks.
Version 2 puts the same idea into plain English.
quantitative, not quantative
Latin. (verb: ‘do’, ‘dare’, ‘dedi’, ‘datum’. ‘Dare’ = to give)
Datum = a given thing or point. A singular noun
Data = given things or points. A plural noun.
In 1. ‘data’ (meaning thingS) requires the plural of the verb: thus ‘identify’.
In 2. ‘datums’ is not Latin. It really not English either. It is a macaronic word (Latin combined with an English plural form)
You give no subject for the sentence so the question of ‘employs’ vs ‘employ’ is open. If the Subject of this verb is singular, then use ‘employs’. If it is plural, then use ‘employ’.
Hope this clarifies matters.
Oh lordy, it’s the data/datum folks. Are these really the fora for such discussions?
There is if you’re talking about geodetic references. Not that anybody here was.