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In the BibLaTeX manual (accessible from the CTAN page), entry types list required and optional fields. For example,

article [...]

Required fields: author,title,journaltitle,year/date

[...]

"year" and "date" are distinct fields but delimited by a slash rather than a comma. I expect this means that either year or date can be used. Is this a correct interpretation? This seems evident but I didn't see it explicitly mentioned anywhere.

Is it also acceptable that year and date can both be used? Or, is it a strict "OR"? I don't see why you'd want this for year/date, but the slash is also used for author/editor, in which case using both seems more reasonable. If this is the case, the slash seems to mean "at least one of".

Bernard
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MattHusz
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1 Answers1

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In general "/" in the manual means the classical logical or (i.e. at least one). So the

author/editor, [...], doi/eprint/url

in the description of @online means that you should have an author or an editor (or both) and at least one of doi, eprint or url (but again, more is obviously fine as well).

But things are slightly more tricky with "date/year". date and year refer to exactly the piece of information about the work (its date of publication). The year field (the same holds for month) is mostly kept for backwards compatibility with BibTeX styles. The preferred way to give the date of publication in biblatex is the date field. That means that usually there is no reason to have both a year and a date field. In fact the year field will be ignored if a date is present and a warning will be issued. So you could have both fields at the same time, but I'd recommend against it. Therefore it is better to read the "/" in "date/year" as an either ... or.

Note that from a style perspective it does not matter if you used year or date in the input, the result is pretty much the same and almost indistinguishable once the data has been read from the .bib file.

In biblatex there is no immediate technical significance of required vs. optional fields apart from Biber's data model verification (-V/--validate-datamodel). In particular styles don't 'know' which fields are required or optional. Those classifications are at most implicit when style authors implement their style.

§2.3.2 Missing and Omissible Data, p. 34 in v3.16 of the biblatex documentation says

The fields marked as ‘required’ in §2.1.1 are not strictly required in all cases. The bibliography styles which come with this package can get by with as little as a title field for most entry types. A book published anonymously, a periodical without an explicit editor, or a software manual without an explicit author should pose no problem as far as the bibliography is concerned. Citation styles, however, may have different requirements. For example, an author-year citation scheme obviously requires an author/editor and a year field.

So I can only recommend to everyone not to get too hung up on whether or not a field is only optional or required. Make sure your entries contain all available and relevant pieces of information. If a 'required' field is missing in an entry that might be an indication that it would be a good idea double check its appearance in citations and the bibliography to see if you are happy with the output, but that's about it. See also How to cite report-like documents that do not have/need an institution?.

moewe
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