SWI Prolog's RDF store is implemented as a C extension. There's a description of the details here [1]. Apparently, it uses skip-lists for indexes. As a curiosi

SWI Prolog's RDF store is implemented as a C extension. There's a description of the details here [1]. Apparently, it uses skip-lists for indexes. As a curiosity... I implemented a very simple toy triplestore in Kotlin that used AVL TreeSets. [2] (only the storage layer, it has no other querying than a simple for-loop like mechanism :-) ). 1: https://github.com/SWI-Prolog/packages-semweb/blob/master/doc/rdfdb.md https://github.com/SWI-Prolog/packages-semweb/blob/master/do... 2: https://gist.github.com/EmmanuelOga/1d52adb79bdb6092fb698ed5b31fa377 https://gist.github.com/EmmanuelOga/1d52adb79bdb6092fb698ed5...