【2025/04/15 12:00】第75回 La Trobe-Kyushu Joint Seminar on Mathematics for Industryを開催します
第75回 La Trobe-Kyushu Joint Seminar on Mathematics for Industryを以下のように行います．
| 日時 | 4月15日（火曜日）12:00 -13:00 |
| Zoom | https://us06web.zoom.us/j/84005961505 |
| Meeting ID | 840 0596 1505 |
| 講演者 | Guillermo Badia (The University of Queensland, Australia) https://sites.google.com/site/guillermobadialogic/home |
| タイトル | Codd’s Theorem for Databases over Semirings |
| 概要 | Codd’s Theorem, a fundamental result of database theory, asserts that relational algebra and relational calculus have the same expressive power on relational databases. We explore Codd’s Theorem for databases over semirings and establish two different versions of this result for such databases: the first version involves the five basic operations of relational algebra, while in the second version the division operation is added to the five basic operations of relational algebra. In both versions, the difference operation of relations is given semantics using semirings with monus, while on the side of relational calculus a limited form of negation is used. The reason for considering these two different versions of Codd’s theorem is that, unlike the case of ordinary relational databases, the division operation need not be expressible in terms of the five basic operations of relational algebra for databases over an arbitrary positive semiring; in fact, we show that this inexpressibility result holds even for bag databases. |
セミナーは昼食時に行いますので，お弁当を食べながら気楽にご参加下さい． 特に大学院生の方にとって，同じ数学でも分野が違う講演を聞く機会はあまり ないと思います．このセミナーは教員が非専門家向けに講演する貴重な機会です． 数理的な視野を広げる意味でも，英語に触れる意味でも，分野に関係なく気軽にご参加いただければと思います．また，意欲のある学部3年生，4年生の参加も大歓迎です．ふらっと覗いてみてください.