Slide 1Data ModelingThe Data ModelSlide 4Versions/Evolution of the E-R ModelSlide 6An Example of an E-R DiagramAn Extended E-R ModelSlide 9Entities and Entity SetsExample: An Entity Set CUSTOMER and Two Entity InstancesSlide 12AttributesRepresenting Entities and Their AttributesVariations of Displaying AttributesSlide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39CardinalityParent and Child EntitiesHAS-A RelationshipsSlide 43Slide 44An Example of Optional ParticipationSlide 46Example of Mandatory ParticipationSlide 48The Three Types of Minimum CardinalityE-R Data Modeling and the Crow’s Foot NotationData Modeling With The Crow’s Foot NotationCrow’s Foot NotationSlide 53Slide 54Slide 55Slide 56Displaying Attributes in E-R DiagramsStrong EntitiesSlide 59ID-Dependent EntitiesID-dependent EntitiesID-Dependent EntitiesWeak Entities (Summary)Weak Entities ExamplesExplanation of the Auto-Model ExampleSome Salient Points Regarding Weak EntitiesSlide 67Slide 68Slide 69Slide 70Slide 71Subtype EntitiesDenoting Supertypes and Subtypes in Our ER DiagramsExplaining the Hiking Club and the Sailing ClubExample Subtype Entity SetsDiscriminatorsSubtypes: IS-A relationshipsCrow’s Foot Nomenclature SummaryAn Example of the Data Modeling ProcessThe College ReportExamining the College ReportPreliminary Data Model from the College ReportThe Department ReportExamining the Department ReportPreliminary Data Model for COLLEGE-DEPARTMENT-PROFESSORThe Evolving E-R Crow’s Foot Data ModelAnd If A Professor May Teach In Several Departments…Appointments of Professors to DepartmentsMaking the Chairperson a RelationshipThe Chairperson RelationshipThe Department/Major ReportExtracting From The Department ReportE-R Model With The STUDENT Entity SetThe Student Admittance LetterExtracting from the Student Admittance LetterThe E-R Model With The Advises RelationshipSlight Refinement to the E-R ModelThe Resulting E-R Model for Highline UniversityDataBase Data Modeling Using the Entity-Relationship ModelData Modeling•Process of creating a logical representation of the structure of the database•The most important task in database developmentThe Data Model•A data model is a plan, or blueprint, for a database design.•A data model is more generalized and abstract than a database design.•It is easier to change a data model than it is to change a database design, so it is the appropriate place to work through conceptual database problems.The Entity Relationship ModelThe Entity-Relationship model is a set of concepts and graphical symbols that can be used to create conceptual schemasDeveloped by Peter Chen of M.I.T. in 1976 in a landmark paper, "The Entity-Relationship Model: Toward a Unified View of Data," ACM Transactions on Database Systems, Vol. 1, No. 1Chen's initial model has been refined over the yearsVersions/Evolution of the E-R ModelOriginal E-R model by Peter Chen (1976)Extended E-R model (1986): added subtypes, now the most widely used E-R model, and what we will use in IS431Information Engineering/IE model (also called the Crow’s Foot model) developed by James Martin in 1990IDEF1X (1994) : national standard by the National Institute of Standards and TechnologyAdditionally:Unified Modeling Language (UML) Style E-R ModelsSemantic Object Data Models (SOMs)The Four Major Components of the Entity Relationship (E-R) ModelEntities (really entity sets)AttributesRelationshipsIdentifiersAn Example of an E-R DiagramThe notation will be explained…An Extended E-R ModelEntities are represented by rectangles.Attributes are represented by ovals, that are connected to the entity by a straight line.Relationships are represented by diamond shaped symbols.The name of the entity (class) or attribute or relationship is usually placed inside the symbol used for that object. (Sometimes, with relationships, the name is placed adjacent.)The Geometric Symbols in an E-R ModelEntities and Entity Sets•An entity set (or class) is something that can be identified and the users want to track–Entity class is a collection of entities described by the entity format in that class–Entity instance is the representation of a particular entity•There are usually many instances of an entity in an entity class•Consider an entity class STUDENT–An entity instance would be a particular student in the entity class, for example, Matthew Jones might be an entity instance•A general notational convention is to CAPITALIZE the entity set’s nameExample: An Entity Set CUSTOMER and Two Entity InstancesRepresenting Entities (Entity Sets) in an E-R ModelAn entity set/class is represented by a rectangle with the name of the entity set/class in the rectangle. STUDENTAttributes•Description of the entity’s characteristics•All instances of a given entity class have the same attributes–Composite attribute: attribute consisting of the group of attributes–Multi-value attributes: attribute with more than one possible valueRepresenting Entities and Their Attributes•Method 1: Place the entity name in a rectangle, and the attributes as ovals/ellipses attached to the rectangle.•Method 2: Place the entity name at the top of a portrait-shaped rectangle, and place the attributes below the entity name in a rectangle.Variations of Displaying AttributesSTUDENTStudent-idLastnameFirstnameA Student Entity Set With Three Attributes(Using Ovals/ellipses)(Can you describe what the entity set STUDENT would look like, if we used Method 2)?Review of AttributesAttributes are the properties that define the entity's characteristicsThe E-R model assumes that all instances of a given entity set have the same attributes.So, for the ER model in the prior slide for STUDENT, instances of STUDENT, such as Henry Gordon, Joyce Johnson, Jeffrey Chan, etc, will each have a Student-ID, a Lastname and a Firstname attribute.IdentifiersIdentifiers are one or more attributes of entity instances which serve to name, or identify, the entity instance.For the STUDENT entity set, identifiers are Student-id and the composite identifier (Last-name, First-name).Composite identifiers are identifiers that consist of two or more attributesIdentifiers are either Unique (identifies one and only one entity) or Non-Unique (identifies a set of entities).We