\begin{frame} \frametitle{Examples} \begin{goal}{} If an attribute of a ternary relationship depends only on two of the entities, this violates BCNF. \end{goal} \begin{exampleblock}{Ternary relationship} \begin{tcenter} \scalebox{.9}{ \begin{tikzpicture}[every edge/.style={link}] \node[entity] (instructor) {Instructors}; \node[entity,xshift=70mm] (course) {Courses}; \node[entity,xshift=35mm,yshift=-20mm] (term) {Terms}; \node[relationship] at($(instructor)!.5!(course)$) (taught) {taught} edge (instructor) edge (course) edge (term); \node[attribute] [at=(taught),shift={(0cm,1.4cm)}] {room} edge (taught); \end{tikzpicture} } \end{tcenter} \pause \medskip If every course is taught only once per term, then attribute room depends only on term and course (but not instructor). \pause \medskip Then the FD $\sql{term},\sql{course} \to \sql{room}$ violates BCNF. \end{exampleblock} \end{frame}