The purpose of this master thesis is to examine a proposal for basic class 4 in UDC, which has been empty since 1964, and to pick out a negotiable subject for that proposal. The proposal is analysed from a theoretical perspective based on principles created by S. R. Ranganathan. Three principles are used. Brevity, Canon of Mnemonics and Decimal fraction device. The questions for this master thesis are: What subjects are suitable to use in basic class 4? What consequences will the proposal have on UDC? Medicine would be the best choice for basic class 4. In the analysis the principles are used to evaluate the formed proposal to basic class 4. The analysis shows that not all of the picked principles are affected if Medicine is moved from basic class 6 to basic class 4. The notation would be shorter and improve UDC:s relation with Brevity. Canon of Mnemonic in Medicine would remain unchanged in the notation and Decimal fraction device would be improved with one more free number in the notation. The proposal would also make it better for the users of UDC because Medicine would be the only class in basic class 4, and the biggest class in UDC, basic class 6, would have one class fewer. UDC maybe still is not logical between the subjects, but the proposal can be a push in right direction to a more logical system.