Query Morphing Example 1

In distance learning, a student searches for information related to a subject matter from the sources. The sources initially specified by the student are the textbooks and class notes provided by the instructor. The query processor finds related reference books and videotaped materials, consequently the sources in the query are updated by the query processor. This is a typical example of incremental query morphing.
Original query:
Select object
From textbook, classnotes
Where object.topic = “binary tree”

Morphed query:
Select object
From textbook, classnotes, reference_book, videotaped_materials
Where object.topic = “binary tree”