Database: scholar_minus_1_0
Question: When did Michael Stonebraker publish his GIS Database paper ?
SQL: select distinct t2.year from paperkeyphrase_keyphrase as t1 join paper as t2 on t1.paperid = t2.paperid join writes as t3 on t2.paperid = t3.paperid join author as t4 on t3.authorid = t4.authorid where t4.authorname = 'michael stonebraker' and t1.keyphrasename = 'gis database' ;