Examples
SELECT x.url, x.title, y.url, y.title FROM Document x SUCH THAT x MENTIONS “Computer Science”, Document y SUCH THAT x = y -- docs within 2 links from something on CS.
SELECT d.url, d.title FROM Document d SUCH THAT “http://www.cs.toronto.edu” = d WHERE d.title CONTAINS “database”; -- docs within 2 links of CS homepage.
MENTIONS: search engine, CONTAINS: checked locally