CREATE TABLE keyphrase (keyphraseid NUMBER, keyphrasename VARCHAR2)
CREATE TABLE paper (paperid NUMBER, title VARCHAR2, venueid NUMBER, year NUMBER, numciting NUMBER, numcitedby NUMBER, journalid NUMBER)
CREATE TABLE journal (journalid NUMBER, journalname VARCHAR2)
CREATE TABLE field (fieldid NUMBER)
CREATE TABLE dataset (datasetid NUMBER, datasetname VARCHAR2)
CREATE TABLE author (authorid NUMBER, authorname VARCHAR2)
CREATE TABLE paperdataset (paperid NUMBER, datasetid NUMBER)
CREATE TABLE venue (venueid NUMBER, venuename VARCHAR2)
CREATE TABLE paperkeyphrase (paperid NUMBER, keyphraseid NUMBER)
CREATE TABLE cite (citingpaperid NUMBER, citedpaperid NUMBER)
CREATE TABLE writes (paperid NUMBER, authorid NUMBER)
CREATE TABLE paperfield (fieldid NUMBER, paperid NUMBER)

What authors wrote papers about Semantic Spaces in 2016 ?
SELECT DISTINCT writes.authorid FROM author, keyphrase, paper, paperkeyphrase, writes WHERE keyphrase.keyphrasename = 'Semantic Spaces' AND paperkeyphrase.keyphraseid = keyphrase.keyphraseid AND paper.paperid = paperkeyphrase.paperid AND paper.year = 2016 AND writes.authorid = author.authorid AND writes.paperid = paper.paperid
SELECT DISTINCT "writes"."authorid" FROM "author" JOIN "writes" ON "author"."authorid" = "writes"."authorid" JOIN "paper" ON "paper"."paperid" = "writes"."paperid" AND "paper"."year" = 2016 JOIN "paperkeyphrase" ON "paper"."paperid" = "paperkeyphrase"."paperid" JOIN "keyphrase" ON "keyphrase"."keyphraseid" = "paperkeyphrase"."keyphraseid" AND "keyphrase"."keyphrasename" = 'Semantic Spaces'