Slide 1Why OO?OO Data ConceptsClassesDefining a ClassWriting and Using MethodsClass HierarchiesSlide 8UML Class Diagrams-1Slide 10UML Diagrams-2ODMG ModelODL-Class DeclarationsSlide 14Slide 15Slide 16Slide 17Slide 18Slide 19ODL-Attribute TypesODL-Structured TypesCollection TypesRelationshipsMethodsSubclassesRelationship ClassesSlide 27KeysOQL-Object Query Language-1OQL-FROM lineOQL-WHERE lineDeveloping an OO DatabaseSlide 33Defining the SchemaCSC 3800 Database Management SystemsTime: 1:30 to 2:20 Meeting Days: MWF Location: Oxendine 1237BTextbook: Databases Illuminated, Author: Catherine M. Ricardo, 2004, Jones & Bartlett PublishersFall 2009Chapter 8The Object-Oriented ModelDr. Chuck LillieWhy OO?Why OO?Traditional relational model does not represent complex data and relationships wellNeed additional support for advanced applicationsOO paradigm widely used for programming OO database provides persistent objects to correspond to temporary objects in programsExamples: Objectivity, GemStone, ObjectStore, VersantOO Data ConceptsOO Data ConceptsAn object has a state and a unique identifier◦Similar to an entity, but has methods in addition to attributes (data elements)◦Objects are encapsulated – data and methods form a unit with restricted access◦Only object’s methods have access to its data◦Object’s interface is visible to outside worldA literal has a state but no identifier – can be atomic (values of built-in types) or structuredClassesClassesA class is a set of objects having the same structure- same variables with the same datatypes, same methods, and same relationships◦Roughly equivalent to an entity type◦Includes data elements, operations and relationships◦Datatypes can be predefined atomic types (integer, real, char, boolean), more complex types, or user-defined typesSet of objects in a class is called the extent (like extension)◦Class extent is roughly equivalent to an entity set◦Objects in the class (instances, object instances, objects) are similar to entity instancesDefining a ClassDefining a ClassDefined by listing components◦Data members (attributes, instance variables)◦Member methods (functions or procedures that belong to the class)◦Relationships that the class participates in Simplified Example:class Person {attribute string name;attribute string address;attribute string phone;void setName(string newName); // methodstring getName( ); //methodrelationship Job hasjob; //relates to Job class}Writing and Using Writing and Using MethodsMethodsMethod written in OO language-Java, C++, etc.Ex:void setName(string newName){self.name = newName;}User’s program may have a Person objectPerson firstPerson = new Person( );Invoke method using Person objectfirstPerson.setName(‘Jack Spratt’ );firstPerson becomes “calling object”, referred to as self in methodClass HierarchiesClass HierarchiesClasses organized into class hierarchies◦Superclasses (base classes and subclasses)◦Each subclass has an isa relationship with its superclass similar to specialization and generalization in the EER modelSubclasses inherit the data members and methods of their superclasses, and may have additional data members and methods of their own Hierarchy diagram-See Figure 8.2◦Represent classes as rectangles◦Connect subclasses to isa triangle, and connect triangle to superclassPersonStudentFacultyUndergraduateGraduateisaisaFigure 8.2 A Class HierarchyUML Class Diagrams-1UML Class Diagrams-1Unified Modeling Language (UML) class diagrams - See Figure 8.5◦Rectangles for classes- 3 sections: class name, attributes, methods ◦Relationships – 2 typesAssociationfor uni- or bi-directional relationships between distinct classes (Ex Student – Faculty relationship)represented by directed line connecting rectangles, with optional name Any descriptive attributes of association in box connected to association line by dotted line (Ex grade in Student - ClassSection)Rolenames can appear on line, but placement is opposite that in E-R (Ex. Student hasAdvisor role appears next to Faculty)AggregationConnects parts to a whole, described by “is part of” (Ex ClassSection to Course)Represented by line with diamond on side of aggregateCan be given a name, or interpreted as “has”◦Reflexive association or reflexive aggregation shown by line back to same class, with rolenames (Ex Course)Person ---------------- pIdnameaddressphone---------------getName( )setName( )Student----------------creditsgpa----------------getCredits( )addCredits( )Faculty--------------ranksalary------------getRank( )getSalary( )Department----------------deptCodedeptNamedeptOfficephone----------------Course--------------cNocTitlecreditsdescription-------------ClassSection-----------------sectionEvaluation-------------dateraterNamerating-------------Undergradute-----------------major----------------getMajor( )setMajor( )Graduate-------------program------------getProgram( )TeachingAssistant--------------fundingSourceannualStipendgradeFigure 8.5 A UML Class DiagramUML Diagrams-2UML Diagrams-2Multiplicity indicators show cardinality & participation◦min..max, but place opposite to placement in E-R; no ( )◦Use * for M; use 1 for 1..1Generalization hierarchies◦Lines connect subclasses to superclass, with triangle at end, pointing to superclass◦Filled triangle for overlapping subclasses◦Open triangle (outline only) for disjoint subclasses◦Can write constraints in curly braces on line near triangle (Ex. {overlapping, optional} near Person class rectangle)Weak entity represented by rectangle with line to strong entity, with discriminator written in box below strong entity (Ex. date is discriminator for Evaluation)ODMG ModelODMG ModelObject Database Management GroupGroup of vendorsDeveloped standards for OO databasesStandards for ◦Object model itself◦Object definition language (ODL)◦Object query language (OQL)◦Language bindings for C++, Java, SmalltalkODL-Class DeclarationsODL-Class DeclarationsSee Figure 8.6Class declarations◦Begin with word class, then classname◦Optional extent and key declarations in parentheses◦List of attributes, methods, and relationships, all enclosed in curly braces extent ◦Set of object instances for that class that are stored in the database at a given time; the extension◦Like the name of the file where the objects in the class are