Is there any guideline to always include a "parent" tag when tagging a question with package/add-on tags?
For instance, there are many tags for specific R packages, such asggplot2, knitr. Check the wiki excerpts:
ggplot2 is an actively maintained open-source chart-drawing library for R, written by Hadley Wickham, based upon the principles of "Grammar of Graphics". It partially replaces R's basic plot and the lattice package, while providing a clean, powerful, orthogonal and fun API.
knitr is an R package for dynamic report generation based on the concept of literate programming.
Does it make sense to have a question tagged any of these but not r?
The same question applies to many other tags, say, numpy for Python, tags "*.js" for Javascript...
Is it valid to edit these questions only to add the "parent" tag?