Re: Some of the specs a missing...
From your set of questions, it's only output EOL that I cannot deduce with total accuracy...
> Is the data file supplied on the command line or will it be present in the same folder as the script?
"[...] read its input from a file called Decathlon.dat and send its input to a file called Decathlon.out."
That looks like "files in the same directory" with the given hardcoded names.
Additionally: "Your program must produce no screen output."
> What is the file encoding of the input and output file? ASCII? ANSI? UTF-x? EBCDIC?
I'd go with ASCII encoding ("letters", "hyphenated"), but UTF-8 would probably work with my code too, as I wouldn't care about what non-space bytes they separate by spaces and tabs. And then the numbers are all in the 7-bit part of ASCII. Who uses ANSI and EBCDIC with Node, Java or Python anyway? That means they're not even options.
> What end of line marker can be expcted? \n \r\n ?
For input I'd just assume \n and treat \r as "whitespace", because the specs allow for trailing whitespace. For output... that's a tricky one, given that "extraneous output will cause an automatic failure".
I'd go with \n for output only because except VB all the others can run on non-Windows platforms (Linux, BSD, Mac) and produce \n EOLs in those environments. They're promoting cloudiness, and they mainly run Linux in there... I also just realised that Swift is Mac-only, so... \n it is then.
> Reagan & REAGAN are the same person? Can we expect a unique key of 1 name per event?
"Names and event abbreviations must be treated as case-insensitive"
"You may assume that there will be no more than one entry in each data set for a given event for a given competitor, and that there will not be more than one competitor with the same name."
That being said... the terms and conditions say "[...] the fastest and most accurate code"... so you if submit something in Python you're guaranteed to not win anything since Java and Swift will just smoke you. Node is fast, but still way behind Java and Swift.