Wikidata, SPARQL, and RDF in general. And I guess semi-relatedly things like Prolog? I recently decided to fiddle with Wikidata, and it is fascinating to be able to query for any part of a statement, not just the value!
In SPARQL you write statements in the form
<thing> <relation> <thing>
But the cool part is that any of those three parts can be extracted, so you can ask things like "what are the cities in <country>", or "what country harbors the city <city>", but most importantly, "how does <city> relate to <country>".
For example, if you wanted to find out all the historical monuments in state capitals of a country (using my home country as an example, also pseudocode for your time's sake):
fetch ?monumentName, ?cityName given
?monument "is called" ?monumentName.
?monument "is located within" ?city.
?city "is capital of" ?state.
?city "is called" ?cityName.
?city "is located within" "Brazil".
In SPARQL you write statements in the form
But the cool part is that any of those three parts can be extracted, so you can ask things like "what are the cities in <country>", or "what country harbors the city <city>", but most importantly, "how does <city> relate to <country>".For example, if you wanted to find out all the historical monuments in state capitals of a country (using my home country as an example, also pseudocode for your time's sake):