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IS 257 – Spring 2004 2004.04.22 - SLIDE 1
Object-Oriented Database Development (Hoffer Chap 15)
University of California, Berkeley
School of Information Management and Systems
SIMS 257: Database Management
IS 257 – Spring 2004 2004.04.22 - SLIDE 2
Lecture Outline
• Review– Object Oriented DBMS– Inverted File and Flat File DBMS– Object-Relational DBMS (revisited)– Intelligent DBMS
• Object Oriented Database Development– Design using UML– Construction with ODL– Querying with OQL
IS 257 – Spring 2004 2004.04.22 - SLIDE 3
Lecture Outline
• Review– Object Oriented DBMS– Inverted File and Flat File DBMS– Object-Relational DBMS (revisited)– Intelligent DBMS
• Object Oriented Database Development– Design using UML– Construction with ODL– Querying with OQL
IS 257 – Spring 2004 2004.04.22 - SLIDE 4
Object-Oriented DBMS Basic Concepts
• Each real-world entity is modeled by an object. Each object is associated with a unique identifier (sometimes call the object ID or OID)
IS 257 – Spring 2004 2004.04.22 - SLIDE 5
Object-Oriented DBMS Basic Concepts
• Each object has a set of instance attributes (or instance variables) and methods.– The value of an attribute can be an object or
set of objects. Thus complex object can be constructed from aggregations of other objects.
– The set of attributes of the object and the set of methods represent the object structure and behavior, respectively
IS 257 – Spring 2004 2004.04.22 - SLIDE 6
Object-Oriented DBMS Basic Concepts
• The attribute values of an object represent the object’s status. – Status is accessed or modified by sending
messages to the object to invoke the corresponding methods
IS 257 – Spring 2004 2004.04.22 - SLIDE 7
Object-Oriented DBMS Basic Concepts
• Objects sharing the same structure and behavior are grouped into classes.– A class represents a template for a set of
similar objects.– Each object is an instance of some class.
IS 257 – Spring 2004 2004.04.22 - SLIDE 8
Object-Oriented DBMS Basic Concepts
• A class can be defined as a specialization of of one or more classes. – A class defined as a specialization is called a
subclass and inherits attributes and methods from its superclass(es).
IS 257 – Spring 2004 2004.04.22 - SLIDE 9
Object-Oriented DBMS Basic Concepts
• An OODBMS is a DBMS that directly supports a model based on the object-oriented paradigm. – Like any DBMS it must provide persistent
storage for objects and their descriptions (schema).
– The system must also provide a language for schema definition and and for manipulation of objects and their schema
– It will usually include a query language, indexing capabilities, etc.
IS 257 – Spring 2004 2004.04.22 - SLIDE 10
Generalization Hierarchy
Employee NoName
AddressDate hired
Date of Birth
employee
Contract No.Date Hired
consultant
Annual SalaryStock Option
Salaried
Hourly Rate
Hourly
calculateAge
AllocateToContractcalculateStockBenefitcalculateWage
IS 257 – Spring 2004 2004.04.22 - SLIDE 11
Inverted File DBMS
• Usually similar to Hierarchic DBMS in record structure– Support for repeating groups of fields and
multiple value fields
• All access is via inverted file indexes to DBS specified fields.
• Examples: ADABAS DBMS from Software AG -- used in the MELVYL system
IS 257 – Spring 2004 2004.04.22 - SLIDE 12
Flat File DBMS
• Data is stored as a simple file of records. – Records usually have a simple structure
• May support indexing of fields in the records.– May also support scanning of the data
• No mechanisms for relating data between files.
• Usually easy to use and simple to set up
IS 257 – Spring 2004 2004.04.22 - SLIDE 13
Object Relational Data Model
• Class, instance, attribute, method, and integrity constraints
• OID per instance• Encapsulation• Multiple inheritance hierarchy of classes• Class references via OID object
references• Set-Valued attributes• Abstract Data Types
IS 257 – Spring 2004 2004.04.22 - SLIDE 14
PostgreSQL Classes
• The fundamental notion in Postgres is that of a class, which is a named collection of object instances. Each instance has the same collection of named attributes, and each attribute is of a specific type. Furthermore, each instance has a permanent object identifier (OID) that is unique throughout the installation. Because SQL syntax refers to tables, we will use the terms table and class interchangeably. Likewise, an SQL row is an instance and SQL columns are attributes.
IS 257 – Spring 2004 2004.04.22 - SLIDE 15
Creating a Class
• You can create a new class by specifying the class name, along with all attribute names and their types:
CREATE TABLE weather ( city varchar(80), temp_lo int, -- low temperature temp_hi int, -- high temperature prcp real, -- precipitation date date);
IS 257 – Spring 2004 2004.04.22 - SLIDE 16
Intelligent Database Systems
• Intelligent DBS are intended to handle more than just data, and may be used in tasks involving large amounts of information where analysis and “discovery” are needed.
The following is based on “Intelligent Databases” by Kamran Parsaye, Mark Chignell, Setrag Khoshafian and Harry WongAI Expert, March 1990, v. 5 no. 3. Pp 38-47
IS 257 – Spring 2004 2004.04.22 - SLIDE 17
Intelligent Database Systems
• They represent the evolution and merging of several technologies:– Automatic Information Discovery– Hypermedia– Object Orientation– Expert Systems– Conventional DBMS
IS 257 – Spring 2004 2004.04.22 - SLIDE 18
Intelligent Database Systems
IntelligentDatabases
ExpertSystems
TraditionalDatabases
Hypermedia
Automaticdiscovery
ObjectOrientation
IS 257 – Spring 2004 2004.04.22 - SLIDE 19
Intelligent Databases
• Intelligent Database Engine– OO support– Inference features– Global optimization– Rule manager– Explanation manager– Transaction manager– Metadata manager– Access module– Multimedia manager
IS 257 – Spring 2004 2004.04.22 - SLIDE 20
Lecture Outline
• Review– Object Oriented DBMS– Inverted File and Flat File DBMS– Object-Relational DBMS (revisited)– Intelligent DBMS
• Object Oriented Database Development– Construction with ODL– Design using UML– Querying with OQL
IS 257 – Spring 2004 2004.04.22 - SLIDE 21
Chapter 15:Chapter 15:Object-Oriented Database Object-Oriented Database
DevelopmentDevelopment
Modern Database Management
6th EditionJeffrey A. Hoffer, Mary B. Prescott, Fred
R. McFadden
This Lecture uses the slides following from www.prenhall.com/hoffer
IS 257 – Spring 2004 2004.04.22 - SLIDE 22
Object Definition Language (ODL)
• Corresponds to SQL’s DDL (Data Definition Language)
• Specify the logical schema for an object-oriented database
• Based on the specifications of Object Database Management Group (ODMG)
IS 257 – Spring 2004 2004.04.22 - SLIDE 23
Defining a Class
• class – keyword for defining classes
• attribute – keyword for attributes
• operations – return type, name, parameters in parentheses
• relationship – keyword for establishing relationship
IS 257 – Spring 2004 2004.04.22 - SLIDE 24
Defining an Attribute
• Value can be either: – Object identifier OR Literal
• Types of literals– Atomic – a constant that cannot be decomposed into
components– Collection – multiple literals or object types – Structure – a fixed number of named elements, each
of which could be a literal or object type
• Attribute ranges– Allowable values for an attribute– enum – for enumerating the allowable values
IS 257 – Spring 2004 2004.04.22 - SLIDE 25
Kinds of Collections
• Set – unordered collection without duplicates
• Bag – unordered collection that may contain duplicates
• List – ordered collection, all the same type
• Array – dynamically sized ordered collection, locatable by position
• Dictionary – unordered sequence of key-value pairs without duplicates
IS 257 – Spring 2004 2004.04.22 - SLIDE 26
Defining Structures
Structure = user-defined type with components
structstruct keyword
Example:struct Address {struct Address {
String street_addressString street_address
String city;String city;
String state;String state;
String zip;String zip;
};};
IS 257 – Spring 2004 2004.04.22 - SLIDE 27
Defining Operations
• Return type
• Name
• Parentheses following the name
• Arguments within the parentheses
IS 257 – Spring 2004 2004.04.22 - SLIDE 28
Defining Relationships
• Only unary and binary relationships allowed• Relationships are bi-directional
– implemented through use of inverse keyword
• ODL relationships are specified:– relationship indicates that class is on many-side– relationship set indicates that class is on one-side
and other class (many) instances unordered– relationship list indicates that class is on one-side
and other class (many) instances ordered
IS 257 – Spring 2004 2004.04.22 - SLIDE 29
Figure 15-1 –UML class diagram for a university database
The following slides illustrate the ODL implementation of this UML diagram
IS 257 – Spring 2004 2004.04.22 - SLIDE 31
Figure 15-2 –ODL Schema for university database
class keyword begins the class definition.Class components enclosed between { and }
IS 257 – Spring 2004 2004.04.22 - SLIDE 32
Figure 15-2 – ODL Schema for university database
attribute has a data type and a name
specify allowable values using enum
IS 257 – Spring 2004 2004.04.22 - SLIDE 33
Figure 15-2 –ODL Schema for university database
extent = the set of all instances of the class
IS 257 – Spring 2004 2004.04.22 - SLIDE 34
Figure 15-2 –ODL Schema for university database
Operation definition: return type, name, and argument list. Arguments include data types and names
IS 257 – Spring 2004 2004.04.22 - SLIDE 35
Figure 15-2 –ODL Schema for university database
relationship sets indicate 1:N relationship to an unordered collection of instances of the other class
inverse establishes the bidirectionality of the relationship
IS 257 – Spring 2004 2004.04.22 - SLIDE 36
Figure 15-2 –ODL Schema for university database
relationship list indicates 1:N relationship to an ordered collection of instances of the other class
IS 257 – Spring 2004 2004.04.22 - SLIDE 37
Figure 15-2 –ODL Schema for university database
relationship indicates N:1 relationship to an instance of the other class
IS 257 – Spring 2004 2004.04.22 - SLIDE 38
Figure 15-3 – UML class diagram for an employee project database
(a) Many-to-many relationship with an association class
Note:In order to capture special features of assignment, this should be converted into two 1:N relationships
IS 257 – Spring 2004 2004.04.22 - SLIDE 39
Figure 15-3 – UML class diagram for an employee project database
(b) Many-to many relationship broken into two one-to-many relationships
class Employee {(extent employees key emp_id) …………. attribute set (string) skills_required;};
Note:key indicates indentifier (candidate key)
Note: attribute set indicates a multivalued attribute
IS 257 – Spring 2004 2004.04.22 - SLIDE 40
Figure 15-4 UML class diagram showing employee generalization
class Employee extends Employee{( ………….
………….} Note:
extends denotes subclassing
IS 257 – Spring 2004 2004.04.22 - SLIDE 41
Figure 15-5 –UML class diagram showing student generalization
abstract class Student extends Employee{( ………….
abstract float calc_tuition();}
Note: abstract operation denotes no method (no implementation) of calc_tuition at the Student level
Note: abstract class denotes non-instantiable (complete constraint)
IS 257 – Spring 2004 2004.04.22 - SLIDE 42
Creating Object Instances
• Specify a tag that will be the object identifier– MBA699 course ();
• Initializing attributes:– Cheryl student (name: “Cheryl Davis”,
dateOfBirth:4/5/77);
• Initializing multivalued attributes:– Dan employee (emp_id: 3678, name: “Dan Bellon”,
skills {“Database design”, “OO Modeling”});
• Establishing links for relationship– Cheryl student (takes: {OOAD99F, Telecom99F,
Java99F});
IS 257 – Spring 2004 2004.04.22 - SLIDE 43
Querying Objects in the OODB
• Object Query Language (OQL)• ODMG standard language• Similar to SQL-92• Some differences:
– Joins use class’s relationship name:• Select x.enrollment from courseofferings x,
x.belongs_to y where y.crse_course = “MBA 664” and x.section = 1;
– Using a set in a query• Select emp_id, name from employees where
“Database Design” in skills;
IS 257 – Spring 2004 2004.04.22 - SLIDE 44
Current ODBMS Products
• Rising popularity due to:– CAD/CAM applications– Geographic information systems– Multimedia– Web-based applications– Increasingly complex data types
• Applications of ODBMS– Bill-of-material– Telecommunications navigation– Health care– Engineering design– Finance and trading