| Informatikai Tanszékcsoport>>> | In English |
Some Results Related to Dense Families of Database Relations
Vu Duc Thi and Nguyen Hoang Son
Abstract:
The dense families of database relations were introduced
by Järvinen [1]. The aim of
this paper is to investigate some new properties of dense
families of database relations, and their applications. That
is, we characterize functional dependencies and minimal keys
in terms of dense families. We give a necessary and
sufficient condition for an abitrary family to be
dense family. We prove
that with a given relation 
the equality set 
is
an dense family whose size is
at most 
,
where 
is the number of tuples
in . We also prove that the
set of all minimal keys of relation is the transversal hypergraph of the
complement of the equality set . We give an effective algorithm finding all
minimal keys of a given relation . We aslo give an algorithm which from a given
relation finds a cover
of functional dependencies that holds in . The complexity of these algorithms is also
esimated.
Footnotes
... ThiInstitute of Information Technology, Vietnamese Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam.
... SonDepartment of Mathematics, College of Sciences, Hue University, Vietnam.