What is the protocol for adding a next-level-up tag in the hierarchy?

I am specifically thinking about the tags and . Structural engineering is a specialty within Civil engineering, so should every question that is tagged with structural-engineering also include the tag civil-engineering?

This similar situation would probably apply to various tags under mechanical and electrical as well.

Related:Don't forget those high level tags


1 Answer 1


I'll give you my take, though some will disagree and I expect we'll continue to evaluate these tagging conventions indefinitely.

I try to follow the following guidelines (and I'm probably less consistent than I'd like to be):

  1. Most questions need at least one "discipline" tag but exceedingly few benefit from as many as three; four shalt thou not count.
  2. If there's a choice of two "discipline" tags and one is seen as the "sub-discipline" of the other (e.g., and ), always use the more specific tag.
  3. Questions belonging to a sub-discipline may or may not benefit from adding the major discipline tag as well.
  4. When there is a judgment call to be made, try to respect the judgment of the question's author, especially one who seems familiar with our existing tags and conventions.

Ideally, the author of the question can decide which discipline(s) their question belongs to. In reality, tags are most important to the users who answer questions. That's who needs to be able to read the context of the question from the tags so that they can browse, follow and filter tags with an expectation of the subject matter they'll encounter.

Worked Example

Possible Hazards of Software Controlled Systems (Ex. Airline GPS/Elevator)?

This question is tagged . As you read the question, think about which tags are most useful for categorizing it. Are there any that you would remove? I've written up my detailed thoughts below, or you can skip directly to the conclusion after the spoiler.

As it happens, this is one of the few questions on the site that I would confidently identify as a software engineering question. That means four out of the five tags on this question are "discipline" tags (not illegal; definitely a warning sign).

The most important tags by far are [software] and [aircraft-design]. Title and first sentence make [software] the obvious choice for a "discipline" tag because that's the perspective from which the question is being asked; the best answer for the OP would come from an expert in that field. The specific applications asked about are airlines and GPS, so they need to be reflected in the tags as well ([gps] would have to be created).

Why not the other three? First of all, forget elevators. The author has already dealt with that example; there's no question asked about elevators, so no need to call the elevator experts.

My first runner-up is [aerospace-engineering]. It's arguably a subdiscipline of both mechanical and electrical engineering, and I always prefer more specificity over less. The question does require some level of familiarity with the systems of an aircraft, so a subject matter expert in this area could be helpful. That said, it's already got a tag for aircraft, and no other aspect of aerospace engineering seems particularly critical here, so I think this one's a judgment call.

My second runner-up is [electrical-engineering]. It's relevant to the GPS aspect of the question, which doesn't have a tag yet, thus no followers. However, while there are plenty of electrical components to aircraft, the question's not about those components, any more than a question about CAD is about motherboards. Another judgment call.

I have no compelling argument for including [mechanical-engineering]. The most specific application is aircraft, which is encompassed by aerospace engineering, which is usually labeled a sub-discipline of mechanical engineering. Let's not treat tags like matroyshka dolls.

In a vacuum, I'd choose , (I've never really been a fan of "-design" in tags) and .

However, given the existing tags, I might simply replace with and respect the author's judgment by leaving in the other "discipline" tags, especially since I'm not a mechanical or electrical engineer myself. It's always a good idea to be less aggressive when editing content outside of your area of expertise.


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