Everything #OpenStreetMap related is welcome: software releases, showing of your work, questions about how to tag something, as long as it has to do with OpenStreetMap or OpenStreetMap-related software.
OpenStreetMap is a map of the world, created by people like you and free to use under an open license.
Join OpenStreetMap and start mapping: https://www.openstreetmap.org/.
There are many communication channels about OSM, many organized around a certain country or region. Discover them on https://openstreetmap.community/
https://mapcomplete.org/ is an easy-to-use website to view, edit and add points (such as shops, restaurants and others)
https://learnosm.org/en/ has a lot of information for beginners too.
a book store with a café
This is easy because the tags don't overlap.
shop=books
amenity=cafe
a café by day and a wine bar by night
I saw something like this before, and they are usually two businesses with different names. I used two separated POIs (points) placed in the same building area to denote them. In this way, I can also put different names, opening_hours etc to the two POIs.
In the case of the café/bar, they are distinctly the same place. It's actually something I've run across several times in different places, usually they're more upscale than your typical café. Pretty good venue for a date that you're not sure how long you want it to last!
it is common practice in the u.s., at least, to use two nodes for big chain drugstores, where the shop, marked chemist, often has wildly different hours from the pharmacy. they have the same name and much of the same info
I would do a node with the following tags:
amenity = cafe
amenity = bar
opening_hours:bar = Mo-Fr 19:00-02:00
opening_hours:cafe = Mo-Fr 09:00-18:00
Read more here:
https://wiki.openstreetmap.org/wiki/Key:bar
I have asked myself the same question a few times. A very common combination here is also shoemaker + key service in one person.