Object-Oriented Database. Lec10

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1 Object-Oriented Database Lec10

2 Object Orientation Object Orientation Set of design and development principles Based on autonomous computer structures known as objects OO Contribution areas Programming Languages Graphical User Interfaces Databases Design Operating Systems 2

3 OO Concepts: Objects Abstract representation of a real-world entity Unique identity Embedded properties Ability to interact with other objects and self OID Unique to that object Assigned by system at moment of object s creation Cannot be changed under any circumstances Can be deleted only if the object is deleted Can never be reused 3

4 Attributes (Instance Variables) Attributes: Known as instance variables in OO environment Domain: Logically groups and describes the set of all possible values that an attribute can have 4

5 Object State Set of values that object s attributes have at a given time Can vary, although its OID remains the same To change the object s state, change the values of the object s attributes To change the object s attribute values, send a message to the object Message will invoke a method 5

6 Messages and Methods Method: Code that performs a specific operation on object s data Protects data from direct and unauthorized access by other objects Used to change the object s attribute values or to return the value of selected object attributes Represent real-world actions 6

7 Classes Collection of similar objects with shared structure (attributes) and behavior (methods) Class instance or object instance Each object in a class 7

8 Object Characteristics 8

9 Class Hierarchy Superclass Subclass Class lattice 9

10 Inheritance Ability of object to inherit the data structure and behavior of classes above it Single inheritance Class has one immediate superclass 10

11 Inheritance (Cont d.) Multiple Class has more than one immediate superclass 11

12 Abstract Data Types (ADT) Describes a set of similar objects Differs from conventional data types Operations are user-defined Uses encapsulation Definitions needed for creation Name Data representation Abstract data type operations and constraints 12

13 Object Classification Simple Only single-valued attributes No attributes refer to other object Composite At least one multivalued attribute No attributes refer to other object Compound At least one attribute that references other object Hybrid Repeating group of attributes At least one refers to other object Associative object 13

14 Simple Examples SEMESTER (SEM_ID, SEM_NAME, SEM_BEGIN_DATE, SEM_END_DATE) Composite MOVIE(MOVIE_ID, MOVIE_NAME, MOVIE_PRICE, MOVIE_TYPE, MOVIE_ACTORS) Compound STUDENT(STU_ID, STU_NAME, MAJOR, ADVISOR) Hybrid INVOICE(INV_#, CUSTOMER, {PRODUCT, UNITS, PRICE}, INV_DATE) Associative ENROLL(STUDENT, CLASS, GRADE)

15 OO vs. E-R Model Components 15

16 Class-Subclass Relationship 16

17 Interobject Relationships Attribute-Class Link Object s attribute references another object Relationship Representation Related classes enclosed in boxes Double line on right side indicates mandatory Connectivity indicated by labeling each box 1:1 1:M M:N M:N with an Intersection Class 17

18 1:1 and 1:M Relationships 18

19 Employee-Dependent Relationship 19

20 Representing the M:N Relationship 20

21 Representing the M:N Relationship with Associated Attributes 21

22 Representing the M:N Relationship with Intersection Class LOCATION: 22

23 Example Assume the following business rules: A course contains many sections, but each section has only one course A section is taught by one professor, but each professor may teach one or more different sections of one or more course A section may contain many students, and each student is enrolled in many sections of different courses. Each section is taught in one room, but each room may be used to teach several different sections of one or more courses A professor advises many students, but a student has only one advisor 23

24 Example Identify and describe the main classes of objects Create the conceptual OO representations 24

25 Example on OO Database Using intersection class to represent the following relationship STUDENT STU_NUM C STU_LNAME C STU_FNAME C STU_ADDRESS C STU_CITY C STU_STATE C STU_ZIPCODE C ADVISOR: 1 PROFESSOR SCHEDULE: M CLASS CLASS COURSE: COURSE PROFESSOR: PROFESSOR ROOM: ROOM ENROLL: STUDENT GRADE N M GRADE N STU_CUM_GPA N STU_SEM_GPA N Note: C = D = N = 25

26 Review (final exam 20%) Relational data model 15% ERD, normalization, database design MySql 15% create, alter, select (group by, order by, having), update, insert aggregate functions (count, avg, max, min, sum) Transaction management 10% Transaction properties, transaction log Concurrency control and crash recovery 35% Potential problem analysis (lost update, uncommitted data, inconsistent retrieval) Locking, two phase locking and deadlock analysis, timestamping Crash recovery (checkpoint, redo, undo) Data warehouse 10% DSS database and star schema Object-oriented databases 15% Question types: Multiple choice 40% QA 60% Weights are only for reference

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