I work a lot with Harmonised System Codes (https://en.wikipedia.org/wiki/Harmonized_System). In a nutshell, the Harmonised System (HS) provides a way to record all goods based trade in and out of a country. Countries also impose tariffs (taxes) and other conditions on goods based off the HS system.
The problem with the HS system is that some of the groupings are not "free standing", meaning that they have words such as "not elsewhere specified", or "includes goods other than those under this HS code."
As a consequence, some analyst will introduce a grouping system on top of the HS. For example, they say that this chunk of HS codes will be summarised as "beef and veal", these codes as "cars" etc. However, many analyst also don't declare what the groupings mean when they publish their research.
There is a Standard International Trade Classification (SITC)(https://en.wikipedia.org/wiki/Standard_International_Trade_Classification) but this does not match well with the HS codes. This means I can't group HS codes by SITC, report the trade values and tariffs in a database.
My question whether the community has come across any grouping system that works with the HS coding system? From my research, I noticed that DG Agri has this system but it is only for agricultural products.
Also on agriculture, the World Trade Organization has a single grouping for "Agriculture" (using Annex 1 of the Agreement on Agriculture) but doesn't split the groupings any further.