dependency function, horn function, BCNF normal form

i was studying the theory of decomposing a relation into many smaller ones using BCNF normal form.

i was following the algorithm provided at http://www.rci.rutgers.edu/~kannan/science/BCNF.pdf

We have a dependency function AB(!C) + C(!A) [read (!A) as A-compliment]

It is said in the document that by adding the term ABC to the above dependency function you get the following HORN function

    C(!A) + D(!B) + AD(!C) + BC(!D)

HOW ???? First of all how does adding ABC to a dependency function yield a horn function?

Note: If the example given is not clear, pls refer to the .pdf file.

Thanks... Received on Tue Jan 29 2002 - 23:27:14 CST