datum_index wiki article

Another (having recently covered the string_id) piece of information crucial to halo modding that people really don't understand or get the concept of. What people on sites like halomods.com (or what used to be it anyway) like to refer to as a "lone id" when talking about tag data, is really just a tag instance's datum_index.

The tag_reference field contains the datum_index along with the group tag of a tag instance. However when it comes to things like predicted resources, only the actual datum_index to the tag instance is needed. This is due to some unique cases in how the value is used. For tag definition purposes, a tag_reference must be used. However, when it comes to post-processed or run-time only fields, a tag instance datum_index is allowable.

So what are you waiting for? You need educated. Better go to school.

Of course, for OpenSauce programmers, some of this knowledge has been available for years already.