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Table 4.6
Negative Intersection of NDB 1 and NDB 2
NDB 1
NDB 2
NDB
NDB NDB
3
1
2
10**
0*10
10**
011*
1*01
011*
000*
*010
000*
0*10
1*01
*010
Table 4.7
Negative Union of NDB 1 and NDB 2
NDB 1
NDB 2
NDB
NDB NDB
3
1
2
10**
0*10
0110
011*
1*01
1001
000*
*010
Table 4.8
Negative Join (
) of NDB 1 and NDB 2
NDB 1
NDB 2
NDB 3
=
NDB 1
NDB 2
10**
0*100
10***
011*
1*011
011**
000*
*0100
000**
0*100
1*011
*0100
input NDBs are placed in the resultant NDB, and can be defi ned as
follows:
NDB
NDB
NDB
{
zz
x
y
,
x
M
y
,
(
x
NDB
y
NDB
)}
3
1
2
1
2
where
=
Coalesce xy
Two strings x and y of length n coalesce into string
z iff x matches y and for all 1
Match x M y : Two strings, x and y , match iff for all i (( x [ i ]
i
=
y [ i ])
=
=
( x [ i ]
*)
( y [ i ]
*))
h erefore, when the two strings in both databases are exactly the same (compar-
ing each bit of the string, i.e., x M y ), then this string is appended into the NDB 3 ,
for example (Table 4.7).
Negative join. h is operation results in the NDB, which contains all the strings
except those that are in the join of two PDBs: DB 1 , DB 2 . An example of nega-
tive join is given in Table 4.8.
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