2.1$$$attribute:$$a$descriptive$characteristic$of$some$object$or$relationship$$domain:$$a$set$of$values$from$which$an$attribute$value$can$be$drawn$from$$entity:$$an$object$in$the$world$$relationship:$$an$association$between$two$or$more$entities$$entity$set:$$an$abstract$group$of$entities$that$are$all$described$by$the$same$attributes$$relationship$set:$$an$abstract$group$of$all$relationships$between$two$or$more$entities$$one<to<many$relationship:$$a$constraint$on$relationship$sets$indicating$that$one$entity$X$can$be$associated$with$many$entities$Y$and$each$entity$Y$can$be$associated$with$at$most$one$entity$X$$many<to<many$relationship:$$a$constraint$on$relationship$sets$indicating$that$each$entity$X$can$be$associated$with$many$entities$Y$and$vice$versa$$participation$constraint:$$a$constraint$on$relationship$sets$indicating$whether$every$entity$in$an$entity$set$must$be$involved$in$some$relationship$in$the$set$$overlap$constraint:$$a$constraint$on$class$hierarchies$indicating$whether$entities$can$be$part$of$more$than$one$subclass$$covering$constraint:$$a$constraint$on$class$hierarchies$indicating$whether$every$entity$in$the$superclass$must$be$included$in$at$least$one$subclass$$weak$entity$set:$$a$set$of$entities$that$are$uniquely$identifiable$only$in$conjunction$with$an$identifying$owner$entity$in$a$separate$entity$set$$aggregation:$$a$“virtual”$entity$set$formed$from$a$relationship$set$and$the$entity$sets$involved$in$the$relationship$set$$2.2$Professors$can$teach$the$same$course$in$several$semesters$and$each$offering$must$be$recorded$$$$$$$Professors$Courses$Semesters$Teaches$Professors$can$teach$the$same$course$in$several$semesters$and$only$the$most$recent$needs$to$be$recorded$$$$$Every$professor$must$teach$some$course$$$$$Every$professor$teaches$exactly$one$course$$$$$Every$professor$teaches$exactly$one$course$and$every$course$must$be$taught$by$some$professor$$$$$Certain$courses$can$be$taught$by$a$team$of$professors$jointly,$but$it$is$possible$that$no$one$professor$in$a$team$can$teach$the$course$$$$$$$$$$$$$$$$$$$Professors$Courses$Teaches$Professors$Courses$Teaches$Professors$Courses$Teaches$Professors$Courses$Teaches$Professors$Teams$Teaches$Member$Courses$$2.3$Professors$Projects$Students$Departments$ssn$name$age$rank$research$num$sponsor$start$date$end$date$budget$num$name$office$ssn$name$age$degree$Chairs$WorksIn$pct$StudiesIn$WorksOn$Manages$WorksOn$Supervises$Advises$advisor$advisee
View Full Document