I work in a field ancillary to scholarly publishing, as a super-aggregator of published scholarly articles, and our systems are reliant on the concept of an "is

I work in a field ancillary to scholarly publishing, as a super-aggregator of published scholarly articles, and our systems are reliant on the concept of an "issue" as a primary key to group articles. With some of these older industries, it's reasonable to assume their systems were built to fit domain models that predate the conception of online-first publication (and the deprecation of "issues").