How "the rights and interests in the intellectual property rights of the scientists and technicians should be protected and the entity achieving the service-related technological results should remunerate, under ...How "the rights and interests in the intellectual property rights of the scientists and technicians should be protected and the entity achieving the service-related technological results should remunerate, under law, those achieving the service-related technological results and those making outstanding contribution to the transfer of the technological results" are important issues encountered in China in its efforts to improve its innovation capacity and build up a new nation. The current legal system in...展开更多
The following problem is called the everywhere-cover problem:“Given a set of dependencies over a database scheme,is the set of dependencies explicitly given for each relation scheme equivalent to the dependencies imp...The following problem is called the everywhere-cover problem:“Given a set of dependencies over a database scheme,is the set of dependencies explicitly given for each relation scheme equivalent to the dependencies implied for that relation scheme?”It is shown that when the everywhere-cover problem has a ‘yes’ answer,examining only the dependencies explicitly given will suffice to test 3NF,BCNF and 4NF of a database scheme.But this does not hold for 2NF.Consequently,in such cases,tests of BCNF and 4NF all take polynomial time.Then a proof is given that test of 3NF of a database scheme is Co-NP-complete,and from this result it is shown that everywhere-cover is also Co-NP-complete when only functional dependencies are allowed.These results lead to doubt the truth of the well believed conjec- ture that no polynomial time algorithm for designing a Iossless BCNF database scheme is likely to exist.展开更多
文摘How "the rights and interests in the intellectual property rights of the scientists and technicians should be protected and the entity achieving the service-related technological results should remunerate, under law, those achieving the service-related technological results and those making outstanding contribution to the transfer of the technological results" are important issues encountered in China in its efforts to improve its innovation capacity and build up a new nation. The current legal system in...
基金Supported by the National Natural Science Foundation of China.
文摘The following problem is called the everywhere-cover problem:“Given a set of dependencies over a database scheme,is the set of dependencies explicitly given for each relation scheme equivalent to the dependencies implied for that relation scheme?”It is shown that when the everywhere-cover problem has a ‘yes’ answer,examining only the dependencies explicitly given will suffice to test 3NF,BCNF and 4NF of a database scheme.But this does not hold for 2NF.Consequently,in such cases,tests of BCNF and 4NF all take polynomial time.Then a proof is given that test of 3NF of a database scheme is Co-NP-complete,and from this result it is shown that everywhere-cover is also Co-NP-complete when only functional dependencies are allowed.These results lead to doubt the truth of the well believed conjec- ture that no polynomial time algorithm for designing a Iossless BCNF database scheme is likely to exist.
