Hi Miles,
I have never had the need to use PIHeadingSets, PIHeadingSet, PIHeadings or PIHeading objects but I believe they are used more within the Batch world - maybe some of our members who are Batch users can shed some light on how they use them. All documentation points to hierarchical use.
In the future world of Batch you will be looking at PI AF and Event Frames, so MDB & PIHeadingSets will be a thing of the past. In fact, in the latest PI Server release you get an AF <-> MDB syncronisation utility so you can start migrating applications to use AF instead of MDB (I wrote a basic MDB->AF conversion utility some time ago). AF is the next generation (but greatly improved) MDB.
All structures I have built within MDB have just used nested PIModules to dictate the hierarchy, with PIProperties describing configuration data and PIAliases the link to the PI tags.
Cheers,
Rhys.
OSIsoft PI System SpecialistsPI consultancy on PI Systems, PISDK, AFSDK, OLEDB etc and PI custom developments. Well pretty much anything to do with PI!