•Assume a virtual schema of the
WWW, e.g.,
–Course(number,
university, title, prof, quarter)
•Every data source on the web
contains the answer to a view over the virtual schema:
•UW database: SELECT number, title,
prof
• FROM Course
• WHERE univ=‘UW’ AND
quarter=‘2/02’
•Stanford
database:
SELECT
number, title, prof, quarter
• FROM Course
• WHERE
univ=‘Stanford’
•User query:
find all professors who teach “database systems”