I guess they used the d tag to get around having to define using the e or a tag, but that's just two lines of code.

And describing what you are identifying is easiest using a hierarchy.

I am identifying a publication. It is a book. It is friction. It is historical.

I am identifying a concept. It is a plan. It is for software. It is for testing.

I am identifying a place. It is a lake. It is in Europe. It is in Germany.

And so on. That also means that you can look for something, without knowing specifically what you are seeking, as each choice opens up more choices.