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Advanced Database ApplicationsAdvanced Database Applications
• Computer-Aided Design (CAD).
• Computer-Aided Manufacturing (CAM).
• Computer-Aided Software Engineering (CASE).
• Network Management Systems.
• Office Information Systems (OIS) and Multimedia Systems.
• Digital Publishing.
• Geographic Information Systems (GIS).
• Interactive and Dynamic Web sites.
• Other applications with complex and interrelated objects and procedural data.
OODBMS
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Weaknesses of RDBMSsWeaknesses of RDBMSs
• Poor Representation of “Real World” Entities.
• Semantic Overloading.
• Poor Support for Integrity and Enterprise Constraints.
• Homogeneous Data Structure.
• Limited Operations.
• Difficulty Handling Recursive Queries.
• Impedance Mismatch.
• Other Problems with RDBMSs:o Transactions are generally short-lived and concurrency control protocols not
suited for long-lived transactions.
o Schema changes are difficult.
o RDBMSs are poor at navigational access.
OODBMS
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Example - Recursive QueryExample - Recursive Query
S005S004S003S002S001S005S005S005S004S004S003
S004S003S002S001NULLS003S002S001S002S001S001
StaffNo
S005S004S003S002S001
S004S003S002S001NULL
MangrsSNo MangrSNoStaffNo
OODBMS
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What is an OODBMS ?What is an OODBMS ?
OODBMS
OODBMS (Object-oriented Database Management System): is a database
with data stored in objects and collections NOT rows and tables.
Object Oriented Concepts:
Abstraction, encapsulation, and information hiding.
Objects and attributes.
Object identity.
Methods and messages.
Classes, subclasses, superclasses, and inheritance.
Overriding, Overloading, Polymorphism and Dynamic Binding.
OODBMS 6
Traditional DBS
•Persistence•Sharing•Transactions•Concurrency Control•Recovery Control•Security•Integrity•Querying
Semantic Data Model
•Generalization•Aggregation
OO Programming
•OID•Encapsulation•Inheritance•Types & Classes•Methods•Complex objects•Polymorphism•Extensibility
Special Requirements
•Versioning•Schema Evolution
OODBMS
OODBMSOODBMS
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AbstractionAbstraction
Abstraction is the process of identifying essential aspects of an entity and
ignoring unimportant properties.
Concentrate on what an object is and what it does, before deciding how to
implement it.
OODBMS
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Encapsulation & Information HidingEncapsulation & Information Hiding
Encapsulation: means that an object contains both data structure and set
of operations used to manipulate it.
Information Hiding: means separating external aspects of an object from
its internal details, which are hidden from outside.
• Allows internal details of an object to be changed without affecting applications
that use it, provided external details remain same.
• Provides data independence.
OODBMS
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ObjectsObjects
Object is a uniquely identifiable entity that contains both:
• the attributes that describe the state of a real-world object,
• and the actions associated with it.
Definition very similar to that of an entity, however, Object encapsulates
both state and behavior; an entity only models state.
Persistent Objects vs. Transient Objects:
• Transient: object’s memory allocated and deallocated by programming language’s runtime system.
• Persistent: object’s storage managed by OODBMS.
OODBMS
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AttributesAttributes
Attributes contain current state of an object:
• Attributes can be classified as simple or complex.
• Simple attribute can be a primitive type such as integer, string, etc.,
which takes on literal values.
• Complex attribute can contain collections and/or references.
• Reference attribute represents relationship.
• An object that contains one or more complex attributes is called a
complex object.
OODBMS
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Object Identity (OID)Object Identity (OID)
Object identifier (OID) assigned to object when it is created that is:
• System-generated.
• Unique to that object.
• Invariant.
• Independent of the values of its attributes (that is, its state).
• Invisible to the user (ideally).
OODBMS
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Object Identity (OID)Object Identity (OID)
In RDBMS, entity identity is value-based: primary key is used to provide
uniqueness.
Primary keys do not provide type of object identity required in OO
systems:
• key only unique within a relation, not across entire system;
• key generally chosen from attributes of relation, making it dependent
on entity state.
OODBMS
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Methods & MessagesMethods & Messages
Method: Defines behavior of an object, as a set of encapsulated
functions.
Message: Request from one object to another asking second object to
execute one of its methods.
OODBMS
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Object Showing Attributes & Object Showing Attributes & MethodsMethods
Attributes
Method 4 Method 3
Method 2Method 1
OODBMS
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ClassesClasses
Classes are blueprints for defining a set of similar objects.
• Objects in a class are called instances.
• Class is also an object with own class attributes and class methods.
• Object created from the same class share the same class attributes
and methods.
OODBMS
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Class Instance Share Attributes & Class Instance Share Attributes & MethodsMethods
BRANCH
BranchNo = B005Street = 22 Deer RdCity = LondonPostcode = SW1 4EH
BranchNo = B007Street = 16 Argyll StCity = AberdeenPostcode = AB2 3SU
BranchNo = B003Street = 163 Main StCity = GlasgowPostcode = G11 9QX
Attributes
branchNostreetcitypostcode
Methods
print()getPostCode()numberOfStaff()
OODBMS
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Subclasses, Superclasses, & Subclasses, Superclasses, & InheritanceInheritance
Inheritance allows one class of objects to be defined as a special case of
a more general class.
•Special cases are subclasses and more general cases are superclasses.
•Process of forming a superclass is generalization; forming a subclass is
specialization.
•Subclass inherits all properties of its superclass and can define its own unique
properties.
•Subclass can redefine inherited methods (overriding).
•Relationship between subclass and superclass known as A KIND OF (AKO)
relationship.
OODBMS
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Subclasses, Superclasses, & Subclasses, Superclasses, & InheritanceInheritance
Types of inheritance: single, multiple, and repeated.
OODBMS
Single Inheritance Multiple Inheritance Repeated Inheritance
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Overriding, Overloading & Overriding, Overloading & PolymorphismPolymorphism
Overriding is the process of redefining a property within a subclass.
Overloading allows name of a method to be reused with a class or across
classes.
Polymorphism means ‘many forms’. Three types: operation, inclusion, and
parametric.
The process of selecting the appropriate method based on an object’s type is called binding.
• If the determination of an object’s type can be deferred until runtime (rather than compile time), the selection is called dynamic binding.
OODBMS
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Complex ObjectsComplex Objects
A Complex object is something that can be viewed as a single object in the
real world but it actually consists of many sub-objects.
Two types of complex objects:
•Unstructured complex objects:
• Their structure hard to determine.
• Requires a large amount of storage.
• BLOB (Binary Large Objects): images & long test strings.
•Structured complex objects:
• Clear structure.
• Sub-objects in A PART-OF (APO) relationship.OODBMS
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Structured Complex ObjectsStructured Complex Objects
The contained object can be handled in one of two ways:
• Contained object can be encapsulated within complex object, accessed
by complex object’s methods.
• Or have its own independent existence, and only an OID is stored in
complex object.
OODBMS
Obj 2
Contains a number of unnamed, homogeneous elements; each can be
instance of atomic type, another collection, or a literal type.
Types of Constructors:
Set: unordered collection of objects without duplicates.
Bag: unordered collection of objects that allows duplicates.
List: ordered collection of objects that allows duplicates.
Array: ordered collection of objects without duplicates.
Dictionary: unordered sequence of key-value pairs without duplicate keys.
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CollectionsCollections
OODBMS
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Commercial OODBMSsCommercial OODBMSs
• GemStone from Gemstone Systems Inc.,
• Itasca from Ibex Knowledge Systems SA,
• Objectivity/DB from Objectivity Inc.,
• ObjectStore from eXcelon Corp.,
• Ontos from Ontos Inc.,
• Poet from Poet Software Corp.,
• Jasmine from Computer Associates/Fujitsu,
• Versant from Versant Object Technology.
OODBMS
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Object Data Management Group (ODMG)Object Data Management Group (ODMG)www.odmg.orgwww.odmg.org
ODMG is an international consortium founded to address object standards.
Major components of ODMG architecture for an OODBMS are:
• Unified Modeling Language (UML).
• Object Model (OM).
• Object Definition Language (ODL).
• Object Query Language (OQL).
• C++, Smalltalk, and Java Language Binding.
OODBMS
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Unified Modeling Language (UML)Unified Modeling Language (UML)
UML is a standard language for specifying, constructing, visualizing, and
documenting the artifacts of a software system.
•Include many structural diagrams (Class, Object diagrams…) and behavioral
diagrams (UseCase, Sequence diagrams…).
•Used to model objects and object relationships.
OODBMS
Class Name
Attribute
Method
MANAGERStaffNosexDOBsalary
increasesalary()
PROPERTYPropertyNostreetcitypostcoderoomstype
1..1 manage 1.1 1..1 offer 1.*
offered-by
Association
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Unified Modeling Language (UML)Unified Modeling Language (UML)
OODBMS
PERSONName FName LName
STAFFStaffNopositionDOBsalary
POWNEROwnerNoaddress
CLIENTClientNotelNOprefTypeMaxRent
MANAGER SALESTAFF
BRANCH
PROPERTYPropertyNoroomsrent
BranchNoaddress
Manages
WorksAt
Offers
ViewsOwns
1
11
M
1
M
1
M M
N
ManagedBy
Has
OwnedBy
IsOfferedBy
ViewedBy
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Object Model (OM)Object Model (OM)
Object Model (OM) provides the data type, type constructors & other
concepts utilized in the ODL to specify the object schema.
•Basic building blocks are object and literal.
•Only an object has a unique identifier and state (current value).
•Literal is a constant values. e.g. “Ahmed”, “123 Main St, London” .
•Behavior defined by set of operations that can be performed on or by
object.
•State defined by values objects carry for a set of attributes of object or
relationships between object and one or more other objects.
OODBMS
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Object Definition Language (ODL)Object Definition Language (ODL)
Object Definition Language (ODL) is a language for defining the specification
of object types for OODBMS. e.g. of ODL definition for DreamHome:
OODBMS
module DreamHome {
Class Branch (extent branchOffices key branchNo)
{
attribute string branchNo;
attribute struct BranchAddress {string street, string city, string postcode} address;
relationship Manager ManagedBy inverse Manager::Manages;
relationship set<SalesStaff> Has inverse SalesStaff::WorksAt;
relationship set<PropertyForRent> Offers inverse PropertyForRent::IsOfferedBy;
void takeOnPropertyForRent(in string propertyNo) raises(propertyAlreadyForRent);
}; };
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Object Query Language (OQL)Object Query Language (OQL)
Object Query Language OQL is a query language for OODBMS.
• Does not provide explicit update operators - leaves this to operations
defined on object types.
OQL can be used for both associative and navigational access:
• Associative query returns collection of objects (like SQL).
• Navigational query accesses individual objects and object relationships
used to navigate from one object to another.
OODBMS
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Object Query Language (OQL)Object Query Language (OQL)
OQL vs. SQL A Simple Example: List the names of the children of
employees working in the sales department.
OODBMS
select
c.fname, c.lname
from
Department d, d.Employee e,
e.Children c
where
d.name = “Sales”;
select
c.fname, c.lname
from
Department d, Employee e,
Children c
where
d.name = “Sales” and
d.deptID = e.deptID and
c.parentID = e.empID;
OQL SQL