Hi!
Could someone tell me what this means? http://wikiba.se/ontology-1.0.owl#directClaim describes it as a "Link between Wikibase Property and direct claim predicate" and the definition in https://www.mediawiki.org/wiki/Wikibase/Indexing/RDF_Dump_Format is similar.
What makes a predicate a direct claim predicate?
Short addition to the great explanations by Daniel - the direct claim(s) have two properties:
1. They always have the simple values (i.e. either URL or literal or bnode), even though full values may contain more information. This means direct claims sometimes are missing secondary information, such as precision, globe, units, etc., but they are simpler to work with and enough for many simpler queries.
2. They include "best ranked" statements - i.e., if the property has preferred rank statements, then only preferred ones will be in direct claims. Otherwise, regular rank ones will be. Deprecated rank claims are never in direct claims. The preferred rank usually is used to describe "current" state of affairs - e.g. current manager of a company, major of a city, population of a country, spouse, etc. - or closest to it.
If you need to see which of the full statements have the same data as direct claims, look for statements with type wikibase:BestRank. This way you can have the same data but with qualifiers, references and full values.