I think it is important that every question has at least one domain tag. These tags make it possible that experts find relevant questions to answer (and searchers find relevant solutions), while secondary tags allow to narrow down.
Examples for tags that could be domain tags in some cases, but are often only secondary tags (e.g., because they only specify the formats that need to be supported):
pdf, html, csv, etc.; and to some extent video, images, etc.
Is it possible to create a Data Explorer query that finds our questions which are tagged only with secondary tags?
(If we can use such a query, and the below list is deemed useful for that purpose, I’ll move it to a separate Meta discussion where it can be curated.)
Incomplete list of secondary tags
How the software must be distributed:
On which platform¹ the software must run:
- ios (ipad-app, iphone-app)
- linux (centos-7, debian, ubuntu)
- windows (windows-7, windows-8, windows-10, windows-xp)
- ~ cross-platform
Of what nature the software must be:
In which programming language the software must be written in:
What technical requirements the software must fulfill:
¹ Tags for a specific software/service (chrome, eclipse, google-apps, skype, amazon, etc.) are similar to platform tags. Questions with these tags should ideally also have a domain tag, but the issue is not as big as with platforms tags, because we get less questions, and the domain is often narrow enough.