In the article "Presenting Wikidata knowledge" [1], I've Been a bit Bold and specified a recipe:
1. Find existing interesting wiki pages in the domain of your application. 2. View the Wikidata information for those pages, choose interesting properties. 3. Associate Wikidata entity IDs with entities of your application. 4. Display their Wikidata information in the user's language. 5. Use the Wikidata "sitelinks" information about the item to provide links to the full Wikipedia (and Wikiquote, Wikivoyage, etc.) article about the entity in the user's language.
But I realize for something like a reference app there won't be Wikidata items for every entity in your app for step 3: not every book in print has a Wikidata item, nor does every musical recording, etc. For those there are already identifiers such as ISBNs and "MusicBrainz release group ID"s (mmm, brains). I assume reference app developers already use these more complete identifiers and so I'm inviting them to add Wikidata entity IDs where available.
I think these other identifiers are all "Wikidata property representing a unique identifier" and there are about 350 of them [2] But surprisingly, I couldn't find an easy way to look up a Wikidata item using these other identifiers.
I found you can do it one-by-one in Wikidata Query [3] and in Wikidata Query Serivce [4] but neither seems amenable to doing a query on the fly "Get me the Wikidata item for each of these 100 ISBNs "2-7071-1620-3", ...
Also, is this a temporary thing? Will Wikidata eventually have items for every book published, every musical recording, etc. and become a superset of all those unique identifiers?
Thanks!
[1] https://www.mediawiki.org/wiki/API:Presenting_Wikidata_knowledge [2] https://www.wikidata.org/wiki/Special:WhatLinksHere/Q19847637?limit=500 [2] https://wdq.wmflabs.org/api?q=string%5B957:%222-7071-1620-3%22%5D and [3] https://query.wikidata.org with the the SPARQL (mmm, sparkly) PREFIX wdt: http://www.wikidata.org/prop/direct/
SELECT ?book WHERE { ?book wdt:P957 "2-7071-1620-3" }