I have "contexts" for:
- Errands
- Shopping
- Home
- iMac (at home)
- Office
- People:Fred
- People:John
Errands and Shopping have "Always Available". People have their location set to their homes (for friends) or offices (for business contacts). When I'm going out and about, I'll check my errands for things I might be able to do when I'm out and about - that's what the context is for. Shopping is specifically for buying stuff from retail stores. Errands is for things like, "renew driver's licence" (because I need to be present in person to have a photo taken).
I've previously used a shopping list application (HandyShopper) which was capable of remembering what aisle every product was in, but that was too much of a pain in the neck to maintain (especially since supermarkets seem to enjoy rearranging their shelves every six months). With HandyShopper I ended up keeping track of "Grocery Stores" as opposed to "Woolworths" or "Coles". Having multiple shops defined meant that I was frequently telling my shopping list application that Corn Flakes were available from this Woolworths but not that one. Or that engine oil was available from this petrol station, but not my regular mechanic.
Maintaining the mapping of what products/services might be available at some location is painful, whatever way you end up doing it. The only way that it would be more useful than burdensome is if someone else did all the work for you (eg: the retailers send you not just a junk mail brochure but a standard-format list of standard product codes for items that they sell at a particular location). I believe that the task is organisationally complex, it's not just that I was somehow doing it wrong.
I just look at the list of things I'm looking to do or buy, and based on my own geographical knowledge of my neighbourhood I plan the outing to complete as many errands as I can in the time I have available. I own my to-do list, my to-do list does not own me.
Pickled Herring? Hrm... they
might be available at the local Woolworths. The task then becomes, "find shop that sells pickled herring" :) I'm certainly not going to write down a list of everything that Woolworths sells in case I might need to buy whoosiwhatsits or framistans in the future.