Semantic Data ModelingWhat Is Conceptual Data Modeling?Bridge the GapData SemanticsConceptual Data Model RevisitedE-R ModelingE-R NotationEntitiesEntity TypesWeak Entity TypesAttributesKey AttributesMore AttributesRelationshipsRelationship DegreesN-ary RelationshipsRelationship AttributeRelationship CardinalityRelationship TypesRecursive Relationship called Supervises with Role NamesEntities associated through two distinct Relationships with Role NamesParticipation ConstraintsStructural ConstraintsMultiplicityOther E-R ModelsPros and Cons of E-RIs-A RelationshipInheritanceER Example – In-class exerciseEER Modeling ExampleSemantic Modeling 1CISSemantic Data Modelingo What is Conceptual Data Modelingo Entity-Relationship (E-R ) Modeling o Limitations of E-R Modelingo Object-oriented Modeling: Another semantic model (discussed later in this course)Semantic Modeling 2CISWhat Is Conceptual Data Modeling?A process that represents the entities, relationships, and activities of an enterprise in terms of a set of abstract concepts of a chosen data model for specific purposes.Enterprise Modeling, Business ModelingConceptualPerceptionof an EnterpriseConceptualPerceptionof an EnterpriseSemantic Modeling 3CISBridge the GapSTUDENT( ID, Name, Age, Address, GPA )INSTRUCTOR ( Emp#, Name, Rank, Dept )COURSE ( Course#, Credits, Title )CLASS ( Emp#, ID, Course#, Time, Room )STUDENT( ID, Name, Age, Address, GPA )INSTRUCTOR ( Emp#, Name, Rank, Dept )COURSE ( Course#, Credits, Title )CLASS ( Emp#, ID, Course#, Time, Room )Semantic Modeling 4CISData Semanticso Static Informationu Data -- Entitiesu Associations -- Relationships among entitieso Dynamic Informationu Activities -- Operations/transactionsu Integrity constraints -- Business rules/regulations and data meaningsSemantic Modeling 5CISConceptual Data Model RevisitedA conceptual data model consists of:o A collection of formal conceptso A set of usage rulesDifferent model has different modeling capabilityConventional (Logical data modeling)Conventional (Logical data modeling)Semantic data modelingSemantic data modelingObject-Oriented data modelingObject-Oriented data modeling-- Hierarchical-- Network-- Relational-- E-R-- EER-- etc.Semantic Modeling 6CISE-R Modelingo Introduced by Peter Chen in 1976o Basic modeling concepts:u Entities, entity types, and attributesu RelationshipsInstructorOfficeAssigned1 1 DepartmentWorks_forN 1 Teaches N M CourseDateLanguageEmp#NameFNameMInitLNameTimeLocationDateSemantic Modeling 7CISE-R NotationEntityRelationshipAttributePrimary KeySemantic Modeling 8CISEntitieso An entity is a conceptual objecto Physically exists4 Usually a noun in requirement specificationCIS 2010CIS 3730JoseAliceSteveAcct CISClassStudentDepartmentSemantic Modeling 9CISEntity Typeso A collection of similar entitieso An abstraction of "physical" entities4 A noun in requirement specifications4 Having "independent" meaningDepartment Department Student Student Course Course AcctCISJoseAliceSteveCIS 3730CIS 2010Semantic Modeling 10CISWeak Entity Typeso Can't exist in DB independentlyo Must be identified by its owneru Owner entity typeu Identify relationshipu Partial keyu Total participationStudent RegistersCar Date1 N Color PNumParking Lot#Semantic Modeling 11CISAttributesProperties or characteristics of entities and entity typesu Attribute values -- Properties of entitiesu Value set - All acceptable attribute valuesu Attributes (definitions) -- Properties of entity types4 A noun or an adjective in requirement specifications4 No "independent" meaningID Jose "123-45-6789"25Student Student AgeSemantic Modeling 12CISKey AttributesOne or a group of attributes that can uniquely identify individual entities of an entity typeu A key refers to one or a group of attributes as a wholeu A key attribute is a component attribute of a keyu Key changes with data semanticsAn entity type may have several qualified keysu Primary key -- One of the candidate keysu Alternate key - Candidate keys not used as the primary keyu Secondary key -- An identifier of records with similar properties of interest4 The primary key attribute(s) is(are) underlinedSemantic Modeling 13CISMore AttributesStudent Student id agenamedegreesFnameMnameLnameo Simple attributeContains atomic values onlyo Composite attribute Has component attributes__________________________________o Single-valued attributeHas exactly one value per entityo Multi-valued attributeContains repeating values per entity__________________________________o Derived attributeAttribute values computed by means of other attributesSalesrepSalesrepFnameMnameLnameEmpNoCommRateCommEarnedSemantic Modeling 14CISRelationshipsAssociations among entitiesu Relationships -- Associations among entities4 Usually a verb in requirement specificationOccurrence Diagram or Semantic NetCourseStudent TakesJoseph Alice Sue Tom Peter . . . CIS2010 CIS3210 CIS3215 CIS3730CIS8140. . . StudentCourseTakesSemantic Modeling 15CISRelationship DegreesThe number of entity types associated with that relationship. Each entity in a relationship is known as a participant.UnarySupervisesEmployee Employee Employee Employee Department Department WorkBinaryn-aryTernaryProject Project Part Part SupplySupplier SupplierSemantic Modeling 16CISN-ary Relationshipso A link must associate with all participantso Cardinality is with respect to individual relationships4 A N-ary relationship is not equivalent to N binary relationshipsSalesperson Order Customer shipsNM1Semantic Modeling 17CISRelationship Attributeo Describes the association4 A adverb or noun in requirement specificationInstructor Course teachessect#timedateroom#Semantic Modeling 18CISRelationship CardinalityHow entities are connected through a relationshipu One-to-One -- An entity of E1 is connected to at most one entity of E2and vice versa.u One-to-Many -- An entity of E1 may be connected to one or more entities of E2, but an entity of E2 can only be mapped to at most one entity of E1.u Many-to-Many -- An entity of E1may be linked to one or more entities of E2, and vice versa.[ ][ ][ ]...abc...xyz...E1E2R11[ ][ ][ ]...abc...xyz...1M...abc...xyz...MNSemantic Modeling 19CISRelationship Types• Recursive Relationship– Relationship type where same entity type participates more than once in different roles.• Relationships may be given role names to indicate purpose that each participating entity type plays in a relationship.Semantic Modeling 20CISRecursive Relationship