Example 1

ER Tutorial 1SET08104 Database SystemsCopyright @ Napier University

Example 1A publishing company produces scientific books on varioussubjects. The books are written by authors who specialize inone particular subject. The company employs editors who, notnecessarily being specialists in a particular area, each take soleresponsibility for editing one or more publications. A publicationcovers essentially one of the specialist subjects and is normallywritten by a single author. When writing a particular book, eachauthor works with on editor, but may submit another work forpublication to be supervised by other editors. To improve theircompetitiveness, the company tries to employ a variety ofauthors, more than one author being a specialist in a particularsubject.

Example 1 - answerSubjectconcernsPublicationedited byis specialised inis written byEditorAuthorworks withAuthor-Editoremploys

Example 2A General Hospital consists of a number of specialized wards(such as Maternity, Oncology, etc). Each ward hosts a numberof patients, who were admitted on the recommendation of theirown GP and confirmed by a consultant employed by theHospital. On admission, the personal details of every patient arerecorded. A separate register is to be held to store theinformation of the tests undertaken and the results of aprescribed treatment. A number of tests may be conducted foreach patient. Each patient is assigned to one leading consultantbut may be examined by another doctor, if required. Doctors arespecialists in some branch of medicine and may be leadingconsultants for a number of patients, not necessarily from thesame ward.

Example 2 – Partial AnswerWardspecialised inSpecialtygivesTestsis admitted toTest-ResultsTreatmentspecialised ingetsfollowsdevisesPatientis diagnosedDiagnosisdiagnosesDoctorrecommendsassigned toGPConsultant

Example 2 – Full answerWardspecialised inSpecialtygivesTestsis admitted toTest-ResultsTreatmentspecialised ingetsfollowsdevisesPatientis diagnosedDiagnosisdiagnosesDoctorGPrecommendsassigned to0Consultant