rules for reasoning about mvds
Download
Skip this Video
Download Presentation
Rules for Reasoning about MVDs

Loading in 2 Seconds...

play fullscreen
1 / 4

Rules for Reasoning about MVDs - PowerPoint PPT Presentation


  • 39 Views
  • Uploaded on

Rules for Reasoning about MVDs. Use to identify the MVDs (e.g., from FD to MVD) which are necessary for the decomposition of a relation into 4NF. V W is X Y with X=V W and XY=W.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Rules for Reasoning about MVDs' - gitel


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
rules for reasoning about mvds
Rules for Reasoning about MVDs
  • Use to identify the MVDs (e.g., from FD to MVD) which are necessary for the decomposition of a relation into 4NF
v w is x y with x v w and x y w
V W is X Y with X=VW and XY=W
  • V W implies that every instance of R can be losslessly decomposed into two relations R1=(V,F1) and R2=(W,F2)
  • X Y implies that for every value of X are independent of the value of Y
v w is x y with x v w and x y w1
V W is X Y with X=VW and XY=W
  • If X Y then X Z for Z  X  Y (trivial)
  • If X Y and Y Z then X Z (transitivity of MVDs)
  • If X Y then X Z for Z = R – (X  Y) (complementation)
  • If X  Y then X Y (FD implication)
algorithm for 4nf decomposition
Algorithm for 4NF decomposition

Similar to BCNF decomposition:

Given R = (R, D) where D contains FDs and MVDs

  • Take X Y violates the 4NF condition
  • Decompose R into R1=(X,D1) and R2=(X(R-Y),D2) where the FDs in D1 and D2 are computed in the same way as in the BCNF decomposition, see note for the computation of the MVDs
ad