the librarian understands the gist of our sketched diagrambut is bit confused by the locate functionality we explain using specific use case where the user is searching for the word "bunniesthe user first sends search request to the catalog the catalog queries its internal list of items and finds book and dvd with "bunniesin the title at this pointthe catalog doesn' care if it is holding dvdbookcdor magazineall items are the sameas far as the catalog is concerned howeverthe user wants to know how to find the physical itemsso the catalog would be remiss if it simply returned list of titles soit calls the locate method on the two items it has uncovered the book' locate method returns dds number that can be used to find the shelf holding the book the dvd is located by returning the genre and title of the dvd the user can then visit the dvd sectionfind the section containing that genreand find the specific dvd as sorted by the titles as we explainwe sketch uml sequence diagram explaining how the various objects are communicatingcatalog bunnies book bunnies dvd user search locate dds number locate genretitle results whereclass diagrams describe the relationships between classesand sequence diagrams describe specific sequences of messages passed between objects the dashed line hanging from each object is lifeline describing the lifetime of the object the wider boxes on each lifeline represent active processing in that object (where there' no boxthe object is basically sitting idlewaiting for something to happenthe horizontal arrows between the lifelines indicate specific messages the solid arrows represent methods being calledwhile the dashed arrows with solid heads represent the method return values